Gait & Posture 41 (2015) 688–693
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Plantar heel pain and foot loading during normal walking§ Justin Sullivan a,*, Joshua Burns c, Roger Adams a, Evangelos Pappas a, Jack Crosbie b a b c
Discipline of Physiotherapy, Faculty of Health Sciences, The University of Sydney, 75 East Street, Lidcombe, NSW 2141, Australia School of Science and Health, The University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia The Children’s Hospital at Westmead, The University of Sydney, NSW, Australia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 June 2014 Received in revised form 22 January 2015 Accepted 26 January 2015
Plantar heel pain is aggravated by weight-bearing, yet limited evidence exists regarding how people with heel pain load their feet during walking. Knowledge of loading patterns in people with plantar heel pain would enhance the understanding of their foot function and assist in developing intervention strategies. Plantar pressure using the Emed-AT platform (Novel Gmbh, Germany) was collected from 198 people with plantar heel pain and 70 asymptomatic controls during normal walking. Maximum force, force– time integral, peak pressure, pressure–time integral and contact time were measured in four quadrants of the heel, the midfoot and the medial and lateral forefoot. The symptomatic group was sub-divided into equal low-pain and high-pain groups using the Foot Health Status Questionnaire pain score. Following age and body mass comparison, multivariate analyses of covariance were performed to compare the heel pain group to the controls, and the low-pain group to the high-pain group, for each loading variable. The heel pain group displayed lower maximum force beneath the heel, lower peak pressure beneath the postero-lateral heel and lower maximum force beneath the medial forefoot. Force–time integrals were lower beneath the posterior heel regions and higher at the lateral forefoot. People with heel pain also had longer midfoot and forefoot contact time. Higher pain level was associated with lower peak pressure and maximum force beneath regions of the heel. Compared to the controls, people with plantar heel pain demonstrated reduced heel loading and modified forefoot loading consistent with a strategy to offload the painful heel. ß 2015 Elsevier B.V. All rights reserved.
Keywords: Walking Plantar pressure Plantar heel pain
1. Introduction Plantar heel pain is the most common musculoskeletal foot condition treated by health professionals [1] and negatively affects the health-related quality of life of those who experience it [2]. The aetiology of plantar heel pain is unclear [3], and while various interventions are utilised in clinical practice [4], limited evidence exists for the effectiveness of any management strategy [2,5]. Plantar heel pain is thought to result from excessive stress at the calcaneal attachment of the plantar fascia due to the repetitive microtrauma associated with persistent load-bearing [6]. Plantar heel pain is; therefore, considered to be mechanical in nature [7] and symptoms are typically aggravated during weight-bearing
§ The study protocol was approved by the University of Sydney Human Research Ethics Committee, Sydney, Australia. The authors certify that no affiliation or financial involvement exists between them and any organisation with a direct interest in the subject matter or materials discussed in the article. The study was funded by the Podiatry Council of New South Wales, Australia. * Corresponding author. Tel.: +61 02 9351 9156. E-mail address: [email protected] (J. Sullivan).
http://dx.doi.org/10.1016/j.gaitpost.2015.01.025 0966-6362/ß 2015 Elsevier B.V. All rights reserved.
[7,8]. Despite this, there are limited and varied reports regarding foot loading during walking in people with heel pain. Evidence exists supporting a reduction in loading of the heel during walking in people with plantar heel pain [9,10], however, rearfoot loading equivalent to asymptomatic participants has been shown in both general [11,12] and athletic heel pain populations [13]. Inconsistent findings exist regarding midfoot and forefoot loading in people with heel pain [9,10,13,14]. Plantar heel pain typically occurs more medially beneath the heel, yet little consideration has been given to loading of medial and lateral regions of the foot in people with this condition. One study has measured medial and lateral foot loading in people with heel pain; however, a specific athletic group was investigated [13]. A greater understanding of load distribution under the foot during walking could provide clearer insight into foot function in the presence of heel pain and assist with the development of more effective intervention strategies. The aim of this study was to examine regional foot loading in people with heel pain compared to asymptomatic control participants. It was hypothesised that people with heel pain would alter the amount of load and contact time in the heel,
J. Sullivan et al. / Gait & Posture 41 (2015) 688–693
midfoot and forefoot. In addition, it was hypothesised that higher levels of heel pain would amplify these alterations. 2. Methods 2.1. Participants 198 people with plantar heel pain and 70 asymptomatic control participants were recruited into the study. Symptomatic participants were included if they had experienced pain under the heel for at least three weeks; were tender on palpation of the medial calcaneal tuberosity and exhibited pain on one of the following circumstances: first step in the morning or after prolonged sitting [7]; during prolonged standing or walking [7]; during running [1]. Asymptomatic participants had no current or previous history of plantar heel pain. Participants were excluded from both groups if they had undergone surgery to the plantar fascia, or had any of the following: systemic arthritis, neurological conditions, lumbar radiculopathy, neurological or vascular compromise of the foot related to diabetes, or any co-existing and currently painful musculoskeletal condition of the lower limb. Each participant attended for data collection on a single occasion, were screened for the presence of heel pain and allocated to either the symptomatic or asymptomatic group. In accordance with approval from the University of Sydney Human Research Ethics Committee, written informed consent was obtained for each participant. 2.2. Severity of heel pain Each participant in the heel pain group completed the Foot Health Status Questionnaire (FHSQ), an instrument which has demonstrated high content, criterion and construct validity, as well as test-retest reliability [15]. The foot pain sub-scale of the FHSQ was selected to represent the level of pain experienced by each participant. It comprises of four questions, answered on a Likert scale, focusing on the type, level and frequency of foot pain. It is then scored out of 100 using questionnaire specific software (FHSQ version 1.03). The heel pain group was then divided into two groups above and below the median pain score, creating a low pain and a high pain sub-group.
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speed. To avoid any alteration of step length due to platform targeting, participants were instructed not to look at the platform during walking trials. Three trials resulting in the recorded step falling entirely within the platform border were saved for analysis. Trials were discarded if the foot contacted the border of the platform, if the participant was seen to change their step pattern, or if they reported the step as feeling inconsistent with their normal gait. Because regional loading of the foot during weightbearing is influenced by body mass [18–21], each participant’s body mass was measured and recorded in kilograms (kg). 2.3.1. Data processing and statistical analyses Pressure data were processed using the Novel-win software package, version 8.07. (Novel Gmbh, Munich Germany). A mask (Fig. 1) was developed using the Creation of Percentage Masks software (Novel Gmbh, Munich Germany), enabling the foot to be divided into 3 sections: heel, midfoot and forefoot. These sections represent anatomically relevant regions of the foot based on skeletal measurements to allow clear and repeatable divisions of all feet [22]. The heel section measured the initial 30% of foot length, the midfoot section the next 20%, and the forefoot the distal 50%. As plantar heel pain is experienced primarily in the anteromedial section of the heel at the site of the medial calcaneal tuberosity, the possibility of altered loading within the heel region itself was considered. The heel was bisected longitudinally and antero-posteriorly into four separate, equal sized quadrants. These were: postero-medial heel, postero-lateral heel, antero-medial heel and antero-lateral heel. Similarly, the medial sided nature of heel pain suggests potential for altered loading in the medial and lateral sides of the entire foot. As such, the forefoot was bisected longitudinally to create the medial forefoot and lateral forefoot regions. Due to the midfoot having a naturally smaller and lateral contact area, it was left as a single region. For each region of the mask, values for maximum force, force– time integral, peak pressure and pressure–time integral were
2.3. Plantar pressure measurement Plantar pressure was recorded from a single limb of each participant to satisfy the independence requirements for statistical analysis. The symptomatic foot was chosen for participants with unilateral heel pain and the most painful side was chosen for those who presented with symptoms bilaterally. In cases where symptoms were equal in both feet, as well as for the control group, the tested limb was chosen randomly. Plantar pressure data was recorded using the Emed-AT platform (Novel Gmbh, Munich Germany), a reliable device [16] with a sensor area of 360 cm 190 cm, housing 1377 sensors, with a resolution of 2 sensors per square centimetre. The dynamic measurement function of the platform commences automatically with foot contact, lasts for 3 s, and collects at a sampling frequency of 25 Hz. Data was collected using the ‘two-step’ method, shown to be reliable in previous plantar pressure research [16,17]. Each participant commenced walking with the contralateral foot, contacted the platform with the second step of the foot being tested and continued walking for two further steps. Participants were given time to familiarise themselves with the process and practise walking over the platform prior to data collection. Participants were instructed to walk at their normal, comfortable
Fig. 1. Mask created using the Creation of Percentage Masks software (Novel, Gmbh, Germany). The heel and midfoot were divided at 30% of foot length. The midfoot and forefoot were divided at 50% of foot length. Longitudinal division of the heel and forefoot regions was achieved by bisecting the foot. The heel was then sub-divided into equal quadrants via antero-posterior bisection of the heel region.
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Table 1 Participant characteristics of the sample. Data are mean (SD). Plantar heel pain (PHP)
Significance
PHP vs. CON p < 0.001* LP vs. HP p = 0.332 PHP vs. CON p = 0.310 LP vs. HP p = 0.198 PHP vs. CON p = 0.491 LP vs. HP p = 0.428 PHP vs. CON p < 0.001* LP vs. HP p = 0.174 PHP vs. CON p < 0.001* LP vs. HP p= 0.279 –
Low pain (LP) n = 97
High pain (HP) n = 101
Total n = 198
Age (years)
54.6 (13.8)
56.6 (13.0)
55.6 (13.4)
48.4 (17.1)
Gender, no (% female) Height (cm)
Female 69/97 (71%) 165.6 (8.4)
Female 63/101 (62%) 166.6 (9.0)
Female 132/198 (67%) 166.1 (8.7)
Female 42/70 (60%) 167.0 (9.7)
Weight (kg)
78.3 (16.3)
81.4 (16.3)
79.9 (16.3)
71.8 (14.1)
BMI (kg/m )
28.5 (5.2)
29.2 (4.9)
28.8 (5.1)
25.6 (3.8)
Pain (FHSQ)
65.5 (12.8)
27.0 (13.5)
45.9 (23.4)
–
2
*
Control (CON) n = 70
p < 0.05.
calculated. Contact time, both absolute and as a percentage of total foot contact duration for each region were also computed. The average of three successful trials was used for statistical analysis. Statistical analyses were performed using SPSS, version 19 (SPSS Inc, Chicago, IL, USA). The heel pain and control groups were first compared on demographic and physical characteristics including age, gender, height and body mass using analyses of variance (ANOVA). Body mass and age have been shown to affect plantar pressure measures [18,23,24]; therefore, any differences between groups in these variables would need to be controlled. Contrasts were used to compare the control group to the entire heel pain group, and then to compare the low pain group to the high pain group. Following this, a multivariate analysis of covariance (MANCOVA) was performed with paired contrasts to compare the heel pain group to the control group, then the lowlevel pain group with the high-level pain group for each of the pressure platform variables.
and redistribution of plantar loads [25]. This; however, is likely to occur only to an extent, so a measure was used to control the influence of excessive body mass. Pressure data, therefore, was analysed separately using a MANCOVA and paired contrasts, with both age and body mass included as covariates. The results of the MANCOVA with paired contrasts for the force and pressure variables are displayed in Table 2. The results of the MANCOVA for the contact time variables are presented in Table 3. Compared to controls, people with heel pain exhibited lower maximum force throughout all regions of the heel and the medial forefoot, as well as lower peak pressure beneath the postero-lateral heel (Fig. 2). Pressure–time integral was unaffected throughout the foot in the presence of heel pain; however, force–time integral was lower beneath the posterior heel and a higher under the lateral forefoot (Fig. 2). Overall, foot contact time did not differ between the heel pain group and the controls. People with heel pain, however, displayed longer contact time over both the midfoot and forefoot. People with heel pain spent a higher percentage of their entire foot contact time over the mid-foot and medial forefoot regions. People with higher levels of heel pain showed lower peak pressure in the anteromedial heel region, and reduced maximum force in the postero-lateral heel compared with those having less pain (Fig. 2). Pain level did not affect maximum force in the medial forefoot. Pressure–time integral and force–time integral did not vary with pain level beneath any region of the foot. Pain level did not influence either of the contact time variables.
3. Results Details of the participants’ age, gender, height and body mass in the heel pain and control groups are displayed in Table 1. The heel pain group were heavier than the control group; therefore, subsequent analyses expressed force data as a percentage of body weight. The heel pain group were also found to be slightly older than the control group. For the MANCOVA including force and contact time variables, age was included as a covariate in order to control for any effects age might have on these measures during walking. Compared with force measures, pressure measures are less closely related to body mass, as increased mass can be accommodated by increased foot dimensions
4. Discussion The main findings of this study are that people with heel pain demonstrate lower peak pressure beneath the postero-lateral heel, lower maximum force throughout the entire heel and lower force– time integral beneath the posterior heel during walking. This is indicative of a strategy to reduce loading beneath the painful heel. Reduction of loading beneath the heel appears likely to be a direct,
Table 2 MANCOVA results for foot loading variables. Data are mean (SD). Contrast
Postero-medial heel
Peak pressure (kPa)
Heel pain vs. control High pain vs. low pain
309 324 304 315
(73) (64) (78) (68)
308 328 304 312
(68)* (68) (69) (66)
302 301 294 310
(62) (55) (56)* (67)
291 296 285 297
(55) (52) (53) (58)
92 85 95 89
Pressure–time integral (kPa ms)
Heel pain vs. control High pain vs. low pain
83.5 80.3 85.2 82.1
(24.5) (17.9) (28.5) (19.6)
82.9 80.8 84.8 81.1
(22.9) (17.9) (26.4) (18.6)
77.6 71.4 78.9 76.5
(22.5) (17.1) (24.9) (19.6)
75.9 70.9 77.3 74.7
(20.8) (16.5) (23.3) (17.9)
26.3 22.2 28.3 24.5
Maximum force (%BW)
Heel pain vs. control High pain vs. low pain
14.1 17.4 13.7 14.5
(3.5)** (4.8) (3.4) (3.5)
20.6 24.4 19.3 21.8
(5.6)** (5.2) (4.6)** (6.4)
16.9 19.5 16.5 17.2
(4.7)** (4.6) (4.6) (4.9)
22.4 25.5 22.2 22.5
(4.9)** (4.5) (5.2) (4.5)
9.50 (7.3) 8.28 (7.5) 10.0 (7.6) 9.0 (7.0)
Force–time integral (%BW ms)
Heel pain vs. control High pain vs. low pain
3.19 3.36 3.25 3.11
(1.0)* (0.9) (1.2) (0.9)
4.14 4.39 4.16 4.12
(1.1)* (1.0) (1.1) (1.0)
4.04 4.21 4.09 4.00
(1.4) (1.0) (1.4) (1.4)
5.54 5.65 5.65 5.44
(1.6) (1.2) (1.7) (1.5)
2.38 1.94 2.60 2.18
* **
p < 0.05. p < 0.01.
Postero-lateral heel
Antero-medial heel
Antero-lateral heel
Midfoot (58) (60) (63) (53) (21.4) (20.8) (25.4) (16.3)
(2.4) (2.0) (2.7) (2.0)
Medial forefoot
Lateral forefoot
478 483 492 464
(121) (142) (135) (103)
374 348 379 369
(84) (78) (89) (80)
168 154 173 163
(47) (48) (48) (40)
138 120 139 138
(36) (38) (36) (36)
59.3 64.3 58.6 60.1
(10.0)* (10.3) (10.8) (9.0)
46.9 45.1 46.4 47.4
(7.2) (9.2) (7.2) (7.1)
20.3 (4.4) 19.4 (3.5) 20.25 (4.4) 20.35 (4.4)
18.3 (3.5)* 16.5 (4.3) 18.13 (3.5) 18.47 (3.6)
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Table 3 MANCOVA results for contact time variables. Data are mean (SD). Contrast
Postero-medial heel
Contact time (ms)
Heel pain vs. control High pain vs. low pain
448 412 462 435
(156) (73) (199) (90)
449 415 461 439
(122) (71) (147) (87)
444 410 457 432
(124) (73) (149) (90)
452 414 465 441
(122) (71) (145) (89)
394 336 408 382
(131)* (118) (141) (119)
676 631 682 672
(99)* (77) (106) (91)
680 633 686 675
(100)* (70) (108) (92)
778 734 789 768
Contact time % (%total)
Heel pain vs. control High pain vs. low pain
56.8 56.1 57.3 56.4
(7.9) (7.6) (8.3) (7.4)
57.2 56.6 57.7 56.8
(7.1) (7.4) (7.2) (6.9)
56.7 55.9 57.4 56.0
(7.6) (7.5) (7.5) (7.5)
57.7 56.4 58.2 57.2
(7.4) (7.2) (7.2) (7.4)
50.4 45.5 51.1 49.6
(12.1)* (14.5) (11.4) (13.0)
87.2 85.9 87.0 87.3
(4.1)* (3.0) (5.2) (2.5)
87.6 86.4 87.6 87.6
(4.1) (2.4) (5.1) (2.7)
100 100 100 100
*
Postero-lateral heel
Antero-medial heel
Antero-lateral heel
Midfoot
Medial forefoot
Lateral forefoot
Total (142) (76) (176) (95)
p < 0.05.
antalgic strategy, carried out to offload the locus of pain. This view is reinforced by the greater reduction in maximum force and peak pressure beneath regions of the heel observed in the high-pain group. Force–time integrals and pressure–time integrals did not differ between high and low pain participants, however, suggesting that further offloading with higher pain levels is achieved via a reduction of maximum loading, but not loading duration. Previous studies have also suggested this antalgic response to plantar heel pain [9,10]. In contrast, however, some studies have
reported no heel loading differences in people with heel pain. The inconsistent findings may reflect methodological differences including smaller samples [12,26,27], a specifically athletic sample that included recovered participants in the heel pain group [13], or comparison to the unaffected limb rather than control participants [11]. Evidence also exists describing an unchanged force–time integral at the heel in people with heel pain [14]; however, these findings were based on the heel impulse being a percentage of the total foot impulse, representing a relative rather than true impulse at the heel.
Fig. 2. Loading comparisons: # decreased; " increased. (A) Control vs heel pain; (B) Low-pain vs high-pain.
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The findings of decreased maximum force in the medial forefoot, combined with a higher force–time integral in the lateral forefoot, suggests an attempt to reduce plantar fascia loading associated with the windlass effect occurring during late stance phase [28,29]. Tension in the plantar fascia increases throughout stance phase, peaking during late stance as the toes extend [30], to increase medial longitudinal arch height and enhance foot stability [31]. Of all the digits of the foot, the hallux has been demonstrated as making the greatest contribution to the windlass effect [28,32]. Reducing maximum force beneath the medial forefoot, including the hallux, reduces tension in the plantar fascia associated with windlass function, consequently reducing pain. This is supported by the higher force–time integral in the lateral forefoot, as an increase in loading in this region would be the natural corollary of unloading the medial side. Reduced ground reaction force during push-off has been reported previously and described as a potential pain reducing strategy in people with heel pain [33]. Our findings suggest a similar strategy, although highlight that offloading occurs primarily in the medial forefoot. Previous studies have reported mixed results with respect to forefoot loading in people with plantar heel pain. Most of these studies; however, have considered the entire forefoot, with or without the toes separated, rather than a division into medial and lateral halves [9,12,14,34]. The data from the present study, however, demonstrates that the forefoot does not behave as a homogeneous unit. One study of recreational runners with plantar heel pain reported no differences in peak pressure or pressure– time integral under the medial or lateral forefoot compared to controls [13]. These results are consistent with our findings regarding forefoot pressure measures and heel pain during walking, however force related variables were not reported. None of the forefoot loading variables differed between the low pain and high pain groups. It may be that with more pain, direct offloading of the heel is prioritised and the postural changes occurring from this make further reduction in forefoot load impossible. In addition, greater load-bearing by the contralateral limb during the double-support phase could explain the lack of further changes in forefoot pressure with higher pain. Plantar pressure measurement of the contralateral limb would be needed to confirm or refute this possibility. Although overall foot contact time did not differ between the heel pain and control groups, people with heel pain displayed higher contact duration for the midfoot and forefoot regions, consistent with previous findings [9]. In addition, the symptomatic participants spent a greater proportion of overall foot contact duration with the midfoot and medial forefoot contacting the ground. These findings could only occur if the forefoot and midfoot make contact earlier during stance. It appears that, in the presence of heel pain, forefoot and midfoot contact is initiated earlier in order to offload the rearfoot. This strategy would reduce the time that the rearfoot spends in sole contact with the ground, ultimately reducing the load placed on the heel. Although there is no consensus on optimum management for plantar heel pain, evidence exists for the effectiveness of foot orthoses as an intervention [1,7,35]. While the mechanism behind the effectiveness of orthoses is not entirely understood [36], reduction in pressure beneath the heel with the use of orthoses has been demonstrated in people with heel pain [36,37]. The current study suggests that people with heel pain adopt a strategy to offload the heel in order to minimise pain, and it is possible that foot orthoses reduce pain by assisting this offloading strategy. Future research is needed to assess whether orthoses influence midfoot and forefoot contact times or restore relative medial and lateral forefoot load distribution. The findings presented should be considered in the light of some study limitations. First, the relative level of accuracy of the
pressure platform used compared to other commercially available models requires consideration. Although the sampling rate of the platform is considered a minimum level to assess walking [38], a higher sampling rate and greater sensors per cm2 would result in greater accuracy in assessment, as suggested in recently published guidelines [39]. It is possible for platforms with lower frequencies to underestimate peaks in pressure or force, and therefore, the results of this study could have been affected by the platform limitations. Second, the comparisons of plantar pressure variables between groups could have been affected by group differences in age and body mass. High body mass index is a risk factor for plantar heel pain [40]; therefore, it is not unexpected that the heel pain group were heavier than control participants. Although these group differences were controlled for in the statistical analyses, a more ideal comparison of regional foot loading would be between groups of equivalent age and body mass. Third, walking speed has been shown to influence plantar pressure distribution, resulting in some recommendations for standardising speed during testing [41]. It was decided that participants should walk at their selfselected, comfortable speed in order to capture their normal foot to ground interaction. While equivalent total contact time was evident between groups, suggesting parity of walking speed, it remains possible that the reductions in loading found in this study could be related to walking speed. Even if this were the case, walking speed reduction may be a more global strategy used by people with heel pain to assist the offloading process [9]. Finally, two participants (1%) reported pain only during running which might have confounded the interpretation of the walking pressure data. In conclusion, people with heel pain display reduced maximum force beneath the heel, reduced peak pressure beneath the posterolateral heel and reduced force–time integral in the posterior heel during walking. In addition, they modify forefoot loading by reducing maximum force beneath the medial forefoot and increasing the force–time integral beneath the lateral forefoot. Higher pain levels resulted in further reductions in maximum force and peak pressure beneath regions of the heel. People with heel pain appear to contact the ground earlier with their midfoot and forefoot, most likely in an attempt to reduce load on the heel. People with plantar heel pain; therefore, adopt strategies aimed at offloading the painful heel during walking. Acknowledgement The study was partially funded by a grant from the Podiatry Council of New South Wales, Australia. Conflict of interest statement The authors certify that no affiliation or financial involvement exists between them and any organisation with a direct interest in the subject matter or materials discussed in the article. References [1] McPoil TG, Martin RL, Cornwall MW, Wukich DK, Irrgang JJ, Godges JJ. Heel pain–plantar fasciitis: clinical practice guildelines linked to the international classification of function, disability, and health from the orthopaedic section of the American Physical Therapy Association. J Orthop Sports Phys Ther 2008;38:A1–8. [2] Irving DB, Cook JL, Young MA, Menz HB. Impact of chronic plantar heel pain on health-related quality of life. J Am Podiatr Med Assoc 2008;98:283–9. [3] League AC. Current concepts review: plantar fasciitis. Foot Ankle Int 2008;29:358–66. [4] Riddle DL, Schappert SM. Volume of ambulatory care visits and patterns of care for patients diagnosed with plantar fasciitis: a national study of medical doctors. Foot Ankle Int/Am Orthop Foot Ankle Soc [and] Swiss Foot Ankle Soc 2004;25:303–10.
J. Sullivan et al. / Gait & Posture 41 (2015) 688–693 [5] Cole C, Seto C, Gazewood J. Plantar fasciitis: evidence-based review of diagnosis and therapy. Am Fam Physician 2005;72:2237–42. [6] Wearing SC, Smeathers JE, Yates B, Sullivan PM, Urry SR, Dubois P. Sagittal movement of the medial longitudinal arch is unchanged in plantar fasciitis. Med Sci Sports Exerc 2004;36:1761–7. [7] Thomas JL, Christensen JC, Kravitz SR, Mendicino RW, Schuberth JM, Vanore JV, et al. The diagnosis and treatment of heel pain: a clinical practice guidelinerevision 2010. J Foot Ankle Surg 2010;49:S1–9. [8] Goff JD, Crawford R. Diagnosis and treatment of plantar fasciitis. Am Fam Physician 2011;84:676–82. [9] Wearing SC, Smeathers JE, Urry SR. The effect of plantar fasciitis on vertical foot-ground reaction force. Clin Orthop Relat Res 2003;17:5–85. [10] Katoh Y, Chao EY, Laughman RK, Schneider E, Morrey BF. Biomechanical analysis of foot function during gait and clinical applications. Clin Orthop Relat Res 1983;2:3–33. [11] Liddle D, Rome K, Howe T. Vertical ground reaction forces in patients with unilateral plantar heel pain – a pilot study. Gait Posture 2000;11:62–6. [12] Wearing SC, Smeathers JE, Sullivan PM, Yates B, Urry SR, Dubois P. Plantar fasciitis: are pain and fascial thickness associated with arch shape and loading. Phys Ther 2007;87:1002–8. [13] Ribeiro AP, Trombini-Souza F, Tessutti VD, Lima FR, Joao SM, Sacco IC. The effects of plantar fasciitis and pain on plantar pressure distribution of recreational runners. Clin Biomech (Bristol Avon) 2011;26:194–9. [14] Bedi HS, Love BR. Differences in impulse distribution in patients with plantar fasciitis. Foot Ankle Int/Am Orthop Foot Ankle Soc [and] Swiss Foot Ankle Soc 1998;19:153–6. [15] Bennett PJ, Patterson C, Wearing S, Baglioni T. Development and validation of a questionnaire designed to measure foot-health status. J Am Podiatr Med Assoc 1998;88:419–28. [16] Gurney JK, Kersting UG, Rosenbaum D. Between-day reliability of repeated plantar pressure distribution measurements in a normal population. Gait Posture 2008;27:706–9. [17] Bryant A, Singer K, Tinley P. Comparison of the reliability of plantar pressure measurements using the two-step and midgait methods of data collection. Foot Ankle Int/Am Orthop Foot Ankle Soc [and] Swiss Foot Ankle Soc 1999;20:646–50. [18] Wearing SC, Hennig EM, Byrne NM, Steele JR, Hills AP. Musculoskeletal disorders associated with obesity: a biomechanical perspective. Obes Rev 2006;7:239–50. [19] Peduzzi de Castro M, Abreu S, Pinto V, Santos R, Machado L, Vaz M, et al. Influence of pressure-relief insoles developed for loaded gait (backpackers and obese people) on plantar pressure distribution and ground reaction forces. Appl Ergon 2014;45:1028–34. [20] Fabris S, Valezi A, de Souza S, Faintuch J, Cecconello I, Junior M. Computerized baropodometry in obese patients. Obes Surg 2006;16:1574–8. [21] Menz HB, Morris ME. Clinical determinants of plantar forces and pressures during walking in older people. Gait Posture 2006;24:229–36. [22] Burns J, Crosbie J, Hunt A, Ouvrier R. The effect of pes cavus on foot pain and plantar pressure. Clin Biomech (Bristol Avon) 2005;20:877–82.
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[23] Morag E, Cavanagh PR. Structural and functional predictors of regional peak pressures under the foot during walking. J Biomech 1999;32:359–70. [24] Scott G, Menz HB, Newcombe L. Age-related differences in foot structure and function. Gait Posture 2007;26:68–75. [25] Hills AP, Hennig EM, Byrne NM, Steele JR. The biomechanics of adiposity – structural and functional limitations of obesity and implications for movement. Obes Rev 2002;3:35–43. [26] Wearing SC, Smeathers JE, Urry SR, Sullivan PM, Yates B, Dubois P. Plantar enthesopathy: thickening of the enthesis is correlated with energy dissipation of the plantar fat pad during walking. Am J Sports Med 2010;38:2522–7. [27] Wearing SC, Smeathers JE, Yates B, Urry SR, Dubois P. Bulk compressive properties of the heel fat pad during walking: a pilot investigation in plantar heel pain. Clin Biomech 2009;24:397–402. [28] Hicks JH. The mechanics of the foot. II. The plantar aponeurosis and the arch. J Anat 1954;88:25–30. [29] Kappel-Bargas A, Woolf RD, Cornwall MW, McPoil TG. The windlass mechanism during normal walking and passive first metatarsalphalangeal joint extension. Clin Biomech 1998;13:190–4. [30] Erdemir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA. Dynamic loading of the plantar aponeurosis in walking. J Bone Jt Surg 2004;86:546–52. [31] Griffin NL, Miller CE, Schmitt D, D’Aout K. Understanding the evolution of the windlass mechanism of the human foot from comparative anatomy: insights, obstacles, and future directions. Am J Phys Anthropol 2015;156:1–10. [32] Cheng H-YK, Lin C-L, Wang H-W, Chou S-W. Finite element analysis of plantar fascia under stretch – the relative contribution of windlass mechanism and Achilles tendon force. J Biomech 2008;41:1937–44. [33] Chang R, Rodrigues PA, Van Emmerik RE, Hamill J. Multi-segment foot kinematics and ground reaction forces during gait of individuals with plantar fasciitis. J Biomech 2014;47:2571–7. [34] Katoh Y, Chao EY, Morrey BF, Laughman RK. Objective technique for evaluating painful heel syndrome and its treatment. Foot Ankle 1983;3:227–37. [35] Landorf KB, Menz HB. Plantar heel pain and fasciitis. Clin Evid 2008;2008. [36] Bonanno DR, Landorf KB, Menz HB. Pressure-relieving properties of various shoe inserts in older people with plantar heel pain. Gait Posture 2011;33:385–9. [37] Chia KK, Suresh S, Kuah A, Ong JL, Phua JM, Seah AL. Comparative trial of the foot pressure patterns between corrective orthotics, formthotics, bone spur pads and flat insoles in patients with chronic plantar fasciitis. Ann Acad Med Singapore 2009;38:869–75. [38] Richards J, Thewlis D. Measurement of force and pressure. In: Richards J, editor. Biomechanics in Clinic and Research. Edinburgh: Churchill Livingstone:Elsevier; 2008. p. 89–101. [39] Giacomozzi C, Keijsers N, Pataky T, Rosenbaum D. International scientific consensus on medical plantar pressure measurement devices: technical requirements and performance. Ann dell’Ist Super Sanita` 2012;48:259–71. [40] Butterworth PA, Landorf KB, Smith SE, Menz HB. The association between body mass index and musculoskeletal foot disorders: a systematic review. Obes Rev 2012;13:630–42. [41] Segal A, Rohr E, Orendurff M, Shofer J, O’Brien M, Sangeorzan B. The effect of walking speed on peak plantar pressure. Foot Ankle Int 2004;25:926–33.
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Plantar heel pain and foot loading during normal walking§ Justin Sullivan a,*, Joshua Burns c, Roger Adams a, Evangelos Pappas a, Jack Crosbie b a b c
Discipline of Physiotherapy, Faculty of Health Sciences, The University of Sydney, 75 East Street, Lidcombe, NSW 2141, Australia School of Science and Health, The University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia The Children’s Hospital at Westmead, The University of Sydney, NSW, Australia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 June 2014 Received in revised form 22 January 2015 Accepted 26 January 2015
Plantar heel pain is aggravated by weight-bearing, yet limited evidence exists regarding how people with heel pain load their feet during walking. Knowledge of loading patterns in people with plantar heel pain would enhance the understanding of their foot function and assist in developing intervention strategies. Plantar pressure using the Emed-AT platform (Novel Gmbh, Germany) was collected from 198 people with plantar heel pain and 70 asymptomatic controls during normal walking. Maximum force, force– time integral, peak pressure, pressure–time integral and contact time were measured in four quadrants of the heel, the midfoot and the medial and lateral forefoot. The symptomatic group was sub-divided into equal low-pain and high-pain groups using the Foot Health Status Questionnaire pain score. Following age and body mass comparison, multivariate analyses of covariance were performed to compare the heel pain group to the controls, and the low-pain group to the high-pain group, for each loading variable. The heel pain group displayed lower maximum force beneath the heel, lower peak pressure beneath the postero-lateral heel and lower maximum force beneath the medial forefoot. Force–time integrals were lower beneath the posterior heel regions and higher at the lateral forefoot. People with heel pain also had longer midfoot and forefoot contact time. Higher pain level was associated with lower peak pressure and maximum force beneath regions of the heel. Compared to the controls, people with plantar heel pain demonstrated reduced heel loading and modified forefoot loading consistent with a strategy to offload the painful heel. ß 2015 Elsevier B.V. All rights reserved.
Keywords: Walking Plantar pressure Plantar heel pain
1. Introduction Plantar heel pain is the most common musculoskeletal foot condition treated by health professionals [1] and negatively affects the health-related quality of life of those who experience it [2]. The aetiology of plantar heel pain is unclear [3], and while various interventions are utilised in clinical practice [4], limited evidence exists for the effectiveness of any management strategy [2,5]. Plantar heel pain is thought to result from excessive stress at the calcaneal attachment of the plantar fascia due to the repetitive microtrauma associated with persistent load-bearing [6]. Plantar heel pain is; therefore, considered to be mechanical in nature [7] and symptoms are typically aggravated during weight-bearing
§ The study protocol was approved by the University of Sydney Human Research Ethics Committee, Sydney, Australia. The authors certify that no affiliation or financial involvement exists between them and any organisation with a direct interest in the subject matter or materials discussed in the article. The study was funded by the Podiatry Council of New South Wales, Australia. * Corresponding author. Tel.: +61 02 9351 9156. E-mail address: [email protected] (J. Sullivan).
http://dx.doi.org/10.1016/j.gaitpost.2015.01.025 0966-6362/ß 2015 Elsevier B.V. All rights reserved.
[7,8]. Despite this, there are limited and varied reports regarding foot loading during walking in people with heel pain. Evidence exists supporting a reduction in loading of the heel during walking in people with plantar heel pain [9,10], however, rearfoot loading equivalent to asymptomatic participants has been shown in both general [11,12] and athletic heel pain populations [13]. Inconsistent findings exist regarding midfoot and forefoot loading in people with heel pain [9,10,13,14]. Plantar heel pain typically occurs more medially beneath the heel, yet little consideration has been given to loading of medial and lateral regions of the foot in people with this condition. One study has measured medial and lateral foot loading in people with heel pain; however, a specific athletic group was investigated [13]. A greater understanding of load distribution under the foot during walking could provide clearer insight into foot function in the presence of heel pain and assist with the development of more effective intervention strategies. The aim of this study was to examine regional foot loading in people with heel pain compared to asymptomatic control participants. It was hypothesised that people with heel pain would alter the amount of load and contact time in the heel,
J. Sullivan et al. / Gait & Posture 41 (2015) 688–693
midfoot and forefoot. In addition, it was hypothesised that higher levels of heel pain would amplify these alterations. 2. Methods 2.1. Participants 198 people with plantar heel pain and 70 asymptomatic control participants were recruited into the study. Symptomatic participants were included if they had experienced pain under the heel for at least three weeks; were tender on palpation of the medial calcaneal tuberosity and exhibited pain on one of the following circumstances: first step in the morning or after prolonged sitting [7]; during prolonged standing or walking [7]; during running [1]. Asymptomatic participants had no current or previous history of plantar heel pain. Participants were excluded from both groups if they had undergone surgery to the plantar fascia, or had any of the following: systemic arthritis, neurological conditions, lumbar radiculopathy, neurological or vascular compromise of the foot related to diabetes, or any co-existing and currently painful musculoskeletal condition of the lower limb. Each participant attended for data collection on a single occasion, were screened for the presence of heel pain and allocated to either the symptomatic or asymptomatic group. In accordance with approval from the University of Sydney Human Research Ethics Committee, written informed consent was obtained for each participant. 2.2. Severity of heel pain Each participant in the heel pain group completed the Foot Health Status Questionnaire (FHSQ), an instrument which has demonstrated high content, criterion and construct validity, as well as test-retest reliability [15]. The foot pain sub-scale of the FHSQ was selected to represent the level of pain experienced by each participant. It comprises of four questions, answered on a Likert scale, focusing on the type, level and frequency of foot pain. It is then scored out of 100 using questionnaire specific software (FHSQ version 1.03). The heel pain group was then divided into two groups above and below the median pain score, creating a low pain and a high pain sub-group.
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speed. To avoid any alteration of step length due to platform targeting, participants were instructed not to look at the platform during walking trials. Three trials resulting in the recorded step falling entirely within the platform border were saved for analysis. Trials were discarded if the foot contacted the border of the platform, if the participant was seen to change their step pattern, or if they reported the step as feeling inconsistent with their normal gait. Because regional loading of the foot during weightbearing is influenced by body mass [18–21], each participant’s body mass was measured and recorded in kilograms (kg). 2.3.1. Data processing and statistical analyses Pressure data were processed using the Novel-win software package, version 8.07. (Novel Gmbh, Munich Germany). A mask (Fig. 1) was developed using the Creation of Percentage Masks software (Novel Gmbh, Munich Germany), enabling the foot to be divided into 3 sections: heel, midfoot and forefoot. These sections represent anatomically relevant regions of the foot based on skeletal measurements to allow clear and repeatable divisions of all feet [22]. The heel section measured the initial 30% of foot length, the midfoot section the next 20%, and the forefoot the distal 50%. As plantar heel pain is experienced primarily in the anteromedial section of the heel at the site of the medial calcaneal tuberosity, the possibility of altered loading within the heel region itself was considered. The heel was bisected longitudinally and antero-posteriorly into four separate, equal sized quadrants. These were: postero-medial heel, postero-lateral heel, antero-medial heel and antero-lateral heel. Similarly, the medial sided nature of heel pain suggests potential for altered loading in the medial and lateral sides of the entire foot. As such, the forefoot was bisected longitudinally to create the medial forefoot and lateral forefoot regions. Due to the midfoot having a naturally smaller and lateral contact area, it was left as a single region. For each region of the mask, values for maximum force, force– time integral, peak pressure and pressure–time integral were
2.3. Plantar pressure measurement Plantar pressure was recorded from a single limb of each participant to satisfy the independence requirements for statistical analysis. The symptomatic foot was chosen for participants with unilateral heel pain and the most painful side was chosen for those who presented with symptoms bilaterally. In cases where symptoms were equal in both feet, as well as for the control group, the tested limb was chosen randomly. Plantar pressure data was recorded using the Emed-AT platform (Novel Gmbh, Munich Germany), a reliable device [16] with a sensor area of 360 cm 190 cm, housing 1377 sensors, with a resolution of 2 sensors per square centimetre. The dynamic measurement function of the platform commences automatically with foot contact, lasts for 3 s, and collects at a sampling frequency of 25 Hz. Data was collected using the ‘two-step’ method, shown to be reliable in previous plantar pressure research [16,17]. Each participant commenced walking with the contralateral foot, contacted the platform with the second step of the foot being tested and continued walking for two further steps. Participants were given time to familiarise themselves with the process and practise walking over the platform prior to data collection. Participants were instructed to walk at their normal, comfortable
Fig. 1. Mask created using the Creation of Percentage Masks software (Novel, Gmbh, Germany). The heel and midfoot were divided at 30% of foot length. The midfoot and forefoot were divided at 50% of foot length. Longitudinal division of the heel and forefoot regions was achieved by bisecting the foot. The heel was then sub-divided into equal quadrants via antero-posterior bisection of the heel region.
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Table 1 Participant characteristics of the sample. Data are mean (SD). Plantar heel pain (PHP)
Significance
PHP vs. CON p < 0.001* LP vs. HP p = 0.332 PHP vs. CON p = 0.310 LP vs. HP p = 0.198 PHP vs. CON p = 0.491 LP vs. HP p = 0.428 PHP vs. CON p < 0.001* LP vs. HP p = 0.174 PHP vs. CON p < 0.001* LP vs. HP p= 0.279 –
Low pain (LP) n = 97
High pain (HP) n = 101
Total n = 198
Age (years)
54.6 (13.8)
56.6 (13.0)
55.6 (13.4)
48.4 (17.1)
Gender, no (% female) Height (cm)
Female 69/97 (71%) 165.6 (8.4)
Female 63/101 (62%) 166.6 (9.0)
Female 132/198 (67%) 166.1 (8.7)
Female 42/70 (60%) 167.0 (9.7)
Weight (kg)
78.3 (16.3)
81.4 (16.3)
79.9 (16.3)
71.8 (14.1)
BMI (kg/m )
28.5 (5.2)
29.2 (4.9)
28.8 (5.1)
25.6 (3.8)
Pain (FHSQ)
65.5 (12.8)
27.0 (13.5)
45.9 (23.4)
–
2
*
Control (CON) n = 70
p < 0.05.
calculated. Contact time, both absolute and as a percentage of total foot contact duration for each region were also computed. The average of three successful trials was used for statistical analysis. Statistical analyses were performed using SPSS, version 19 (SPSS Inc, Chicago, IL, USA). The heel pain and control groups were first compared on demographic and physical characteristics including age, gender, height and body mass using analyses of variance (ANOVA). Body mass and age have been shown to affect plantar pressure measures [18,23,24]; therefore, any differences between groups in these variables would need to be controlled. Contrasts were used to compare the control group to the entire heel pain group, and then to compare the low pain group to the high pain group. Following this, a multivariate analysis of covariance (MANCOVA) was performed with paired contrasts to compare the heel pain group to the control group, then the lowlevel pain group with the high-level pain group for each of the pressure platform variables.
and redistribution of plantar loads [25]. This; however, is likely to occur only to an extent, so a measure was used to control the influence of excessive body mass. Pressure data, therefore, was analysed separately using a MANCOVA and paired contrasts, with both age and body mass included as covariates. The results of the MANCOVA with paired contrasts for the force and pressure variables are displayed in Table 2. The results of the MANCOVA for the contact time variables are presented in Table 3. Compared to controls, people with heel pain exhibited lower maximum force throughout all regions of the heel and the medial forefoot, as well as lower peak pressure beneath the postero-lateral heel (Fig. 2). Pressure–time integral was unaffected throughout the foot in the presence of heel pain; however, force–time integral was lower beneath the posterior heel and a higher under the lateral forefoot (Fig. 2). Overall, foot contact time did not differ between the heel pain group and the controls. People with heel pain, however, displayed longer contact time over both the midfoot and forefoot. People with heel pain spent a higher percentage of their entire foot contact time over the mid-foot and medial forefoot regions. People with higher levels of heel pain showed lower peak pressure in the anteromedial heel region, and reduced maximum force in the postero-lateral heel compared with those having less pain (Fig. 2). Pain level did not affect maximum force in the medial forefoot. Pressure–time integral and force–time integral did not vary with pain level beneath any region of the foot. Pain level did not influence either of the contact time variables.
3. Results Details of the participants’ age, gender, height and body mass in the heel pain and control groups are displayed in Table 1. The heel pain group were heavier than the control group; therefore, subsequent analyses expressed force data as a percentage of body weight. The heel pain group were also found to be slightly older than the control group. For the MANCOVA including force and contact time variables, age was included as a covariate in order to control for any effects age might have on these measures during walking. Compared with force measures, pressure measures are less closely related to body mass, as increased mass can be accommodated by increased foot dimensions
4. Discussion The main findings of this study are that people with heel pain demonstrate lower peak pressure beneath the postero-lateral heel, lower maximum force throughout the entire heel and lower force– time integral beneath the posterior heel during walking. This is indicative of a strategy to reduce loading beneath the painful heel. Reduction of loading beneath the heel appears likely to be a direct,
Table 2 MANCOVA results for foot loading variables. Data are mean (SD). Contrast
Postero-medial heel
Peak pressure (kPa)
Heel pain vs. control High pain vs. low pain
309 324 304 315
(73) (64) (78) (68)
308 328 304 312
(68)* (68) (69) (66)
302 301 294 310
(62) (55) (56)* (67)
291 296 285 297
(55) (52) (53) (58)
92 85 95 89
Pressure–time integral (kPa ms)
Heel pain vs. control High pain vs. low pain
83.5 80.3 85.2 82.1
(24.5) (17.9) (28.5) (19.6)
82.9 80.8 84.8 81.1
(22.9) (17.9) (26.4) (18.6)
77.6 71.4 78.9 76.5
(22.5) (17.1) (24.9) (19.6)
75.9 70.9 77.3 74.7
(20.8) (16.5) (23.3) (17.9)
26.3 22.2 28.3 24.5
Maximum force (%BW)
Heel pain vs. control High pain vs. low pain
14.1 17.4 13.7 14.5
(3.5)** (4.8) (3.4) (3.5)
20.6 24.4 19.3 21.8
(5.6)** (5.2) (4.6)** (6.4)
16.9 19.5 16.5 17.2
(4.7)** (4.6) (4.6) (4.9)
22.4 25.5 22.2 22.5
(4.9)** (4.5) (5.2) (4.5)
9.50 (7.3) 8.28 (7.5) 10.0 (7.6) 9.0 (7.0)
Force–time integral (%BW ms)
Heel pain vs. control High pain vs. low pain
3.19 3.36 3.25 3.11
(1.0)* (0.9) (1.2) (0.9)
4.14 4.39 4.16 4.12
(1.1)* (1.0) (1.1) (1.0)
4.04 4.21 4.09 4.00
(1.4) (1.0) (1.4) (1.4)
5.54 5.65 5.65 5.44
(1.6) (1.2) (1.7) (1.5)
2.38 1.94 2.60 2.18
* **
p < 0.05. p < 0.01.
Postero-lateral heel
Antero-medial heel
Antero-lateral heel
Midfoot (58) (60) (63) (53) (21.4) (20.8) (25.4) (16.3)
(2.4) (2.0) (2.7) (2.0)
Medial forefoot
Lateral forefoot
478 483 492 464
(121) (142) (135) (103)
374 348 379 369
(84) (78) (89) (80)
168 154 173 163
(47) (48) (48) (40)
138 120 139 138
(36) (38) (36) (36)
59.3 64.3 58.6 60.1
(10.0)* (10.3) (10.8) (9.0)
46.9 45.1 46.4 47.4
(7.2) (9.2) (7.2) (7.1)
20.3 (4.4) 19.4 (3.5) 20.25 (4.4) 20.35 (4.4)
18.3 (3.5)* 16.5 (4.3) 18.13 (3.5) 18.47 (3.6)
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Table 3 MANCOVA results for contact time variables. Data are mean (SD). Contrast
Postero-medial heel
Contact time (ms)
Heel pain vs. control High pain vs. low pain
448 412 462 435
(156) (73) (199) (90)
449 415 461 439
(122) (71) (147) (87)
444 410 457 432
(124) (73) (149) (90)
452 414 465 441
(122) (71) (145) (89)
394 336 408 382
(131)* (118) (141) (119)
676 631 682 672
(99)* (77) (106) (91)
680 633 686 675
(100)* (70) (108) (92)
778 734 789 768
Contact time % (%total)
Heel pain vs. control High pain vs. low pain
56.8 56.1 57.3 56.4
(7.9) (7.6) (8.3) (7.4)
57.2 56.6 57.7 56.8
(7.1) (7.4) (7.2) (6.9)
56.7 55.9 57.4 56.0
(7.6) (7.5) (7.5) (7.5)
57.7 56.4 58.2 57.2
(7.4) (7.2) (7.2) (7.4)
50.4 45.5 51.1 49.6
(12.1)* (14.5) (11.4) (13.0)
87.2 85.9 87.0 87.3
(4.1)* (3.0) (5.2) (2.5)
87.6 86.4 87.6 87.6
(4.1) (2.4) (5.1) (2.7)
100 100 100 100
*
Postero-lateral heel
Antero-medial heel
Antero-lateral heel
Midfoot
Medial forefoot
Lateral forefoot
Total (142) (76) (176) (95)
p < 0.05.
antalgic strategy, carried out to offload the locus of pain. This view is reinforced by the greater reduction in maximum force and peak pressure beneath regions of the heel observed in the high-pain group. Force–time integrals and pressure–time integrals did not differ between high and low pain participants, however, suggesting that further offloading with higher pain levels is achieved via a reduction of maximum loading, but not loading duration. Previous studies have also suggested this antalgic response to plantar heel pain [9,10]. In contrast, however, some studies have
reported no heel loading differences in people with heel pain. The inconsistent findings may reflect methodological differences including smaller samples [12,26,27], a specifically athletic sample that included recovered participants in the heel pain group [13], or comparison to the unaffected limb rather than control participants [11]. Evidence also exists describing an unchanged force–time integral at the heel in people with heel pain [14]; however, these findings were based on the heel impulse being a percentage of the total foot impulse, representing a relative rather than true impulse at the heel.
Fig. 2. Loading comparisons: # decreased; " increased. (A) Control vs heel pain; (B) Low-pain vs high-pain.
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The findings of decreased maximum force in the medial forefoot, combined with a higher force–time integral in the lateral forefoot, suggests an attempt to reduce plantar fascia loading associated with the windlass effect occurring during late stance phase [28,29]. Tension in the plantar fascia increases throughout stance phase, peaking during late stance as the toes extend [30], to increase medial longitudinal arch height and enhance foot stability [31]. Of all the digits of the foot, the hallux has been demonstrated as making the greatest contribution to the windlass effect [28,32]. Reducing maximum force beneath the medial forefoot, including the hallux, reduces tension in the plantar fascia associated with windlass function, consequently reducing pain. This is supported by the higher force–time integral in the lateral forefoot, as an increase in loading in this region would be the natural corollary of unloading the medial side. Reduced ground reaction force during push-off has been reported previously and described as a potential pain reducing strategy in people with heel pain [33]. Our findings suggest a similar strategy, although highlight that offloading occurs primarily in the medial forefoot. Previous studies have reported mixed results with respect to forefoot loading in people with plantar heel pain. Most of these studies; however, have considered the entire forefoot, with or without the toes separated, rather than a division into medial and lateral halves [9,12,14,34]. The data from the present study, however, demonstrates that the forefoot does not behave as a homogeneous unit. One study of recreational runners with plantar heel pain reported no differences in peak pressure or pressure– time integral under the medial or lateral forefoot compared to controls [13]. These results are consistent with our findings regarding forefoot pressure measures and heel pain during walking, however force related variables were not reported. None of the forefoot loading variables differed between the low pain and high pain groups. It may be that with more pain, direct offloading of the heel is prioritised and the postural changes occurring from this make further reduction in forefoot load impossible. In addition, greater load-bearing by the contralateral limb during the double-support phase could explain the lack of further changes in forefoot pressure with higher pain. Plantar pressure measurement of the contralateral limb would be needed to confirm or refute this possibility. Although overall foot contact time did not differ between the heel pain and control groups, people with heel pain displayed higher contact duration for the midfoot and forefoot regions, consistent with previous findings [9]. In addition, the symptomatic participants spent a greater proportion of overall foot contact duration with the midfoot and medial forefoot contacting the ground. These findings could only occur if the forefoot and midfoot make contact earlier during stance. It appears that, in the presence of heel pain, forefoot and midfoot contact is initiated earlier in order to offload the rearfoot. This strategy would reduce the time that the rearfoot spends in sole contact with the ground, ultimately reducing the load placed on the heel. Although there is no consensus on optimum management for plantar heel pain, evidence exists for the effectiveness of foot orthoses as an intervention [1,7,35]. While the mechanism behind the effectiveness of orthoses is not entirely understood [36], reduction in pressure beneath the heel with the use of orthoses has been demonstrated in people with heel pain [36,37]. The current study suggests that people with heel pain adopt a strategy to offload the heel in order to minimise pain, and it is possible that foot orthoses reduce pain by assisting this offloading strategy. Future research is needed to assess whether orthoses influence midfoot and forefoot contact times or restore relative medial and lateral forefoot load distribution. The findings presented should be considered in the light of some study limitations. First, the relative level of accuracy of the
pressure platform used compared to other commercially available models requires consideration. Although the sampling rate of the platform is considered a minimum level to assess walking [38], a higher sampling rate and greater sensors per cm2 would result in greater accuracy in assessment, as suggested in recently published guidelines [39]. It is possible for platforms with lower frequencies to underestimate peaks in pressure or force, and therefore, the results of this study could have been affected by the platform limitations. Second, the comparisons of plantar pressure variables between groups could have been affected by group differences in age and body mass. High body mass index is a risk factor for plantar heel pain [40]; therefore, it is not unexpected that the heel pain group were heavier than control participants. Although these group differences were controlled for in the statistical analyses, a more ideal comparison of regional foot loading would be between groups of equivalent age and body mass. Third, walking speed has been shown to influence plantar pressure distribution, resulting in some recommendations for standardising speed during testing [41]. It was decided that participants should walk at their selfselected, comfortable speed in order to capture their normal foot to ground interaction. While equivalent total contact time was evident between groups, suggesting parity of walking speed, it remains possible that the reductions in loading found in this study could be related to walking speed. Even if this were the case, walking speed reduction may be a more global strategy used by people with heel pain to assist the offloading process [9]. Finally, two participants (1%) reported pain only during running which might have confounded the interpretation of the walking pressure data. In conclusion, people with heel pain display reduced maximum force beneath the heel, reduced peak pressure beneath the posterolateral heel and reduced force–time integral in the posterior heel during walking. In addition, they modify forefoot loading by reducing maximum force beneath the medial forefoot and increasing the force–time integral beneath the lateral forefoot. Higher pain levels resulted in further reductions in maximum force and peak pressure beneath regions of the heel. People with heel pain appear to contact the ground earlier with their midfoot and forefoot, most likely in an attempt to reduce load on the heel. People with plantar heel pain; therefore, adopt strategies aimed at offloading the painful heel during walking. Acknowledgement The study was partially funded by a grant from the Podiatry Council of New South Wales, Australia. Conflict of interest statement The authors certify that no affiliation or financial involvement exists between them and any organisation with a direct interest in the subject matter or materials discussed in the article. References [1] McPoil TG, Martin RL, Cornwall MW, Wukich DK, Irrgang JJ, Godges JJ. Heel pain–plantar fasciitis: clinical practice guildelines linked to the international classification of function, disability, and health from the orthopaedic section of the American Physical Therapy Association. J Orthop Sports Phys Ther 2008;38:A1–8. [2] Irving DB, Cook JL, Young MA, Menz HB. Impact of chronic plantar heel pain on health-related quality of life. J Am Podiatr Med Assoc 2008;98:283–9. [3] League AC. Current concepts review: plantar fasciitis. Foot Ankle Int 2008;29:358–66. [4] Riddle DL, Schappert SM. Volume of ambulatory care visits and patterns of care for patients diagnosed with plantar fasciitis: a national study of medical doctors. Foot Ankle Int/Am Orthop Foot Ankle Soc [and] Swiss Foot Ankle Soc 2004;25:303–10.
J. Sullivan et al. / Gait & Posture 41 (2015) 688–693 [5] Cole C, Seto C, Gazewood J. Plantar fasciitis: evidence-based review of diagnosis and therapy. Am Fam Physician 2005;72:2237–42. [6] Wearing SC, Smeathers JE, Yates B, Sullivan PM, Urry SR, Dubois P. Sagittal movement of the medial longitudinal arch is unchanged in plantar fasciitis. Med Sci Sports Exerc 2004;36:1761–7. [7] Thomas JL, Christensen JC, Kravitz SR, Mendicino RW, Schuberth JM, Vanore JV, et al. The diagnosis and treatment of heel pain: a clinical practice guidelinerevision 2010. J Foot Ankle Surg 2010;49:S1–9. [8] Goff JD, Crawford R. Diagnosis and treatment of plantar fasciitis. Am Fam Physician 2011;84:676–82. [9] Wearing SC, Smeathers JE, Urry SR. The effect of plantar fasciitis on vertical foot-ground reaction force. Clin Orthop Relat Res 2003;17:5–85. [10] Katoh Y, Chao EY, Laughman RK, Schneider E, Morrey BF. Biomechanical analysis of foot function during gait and clinical applications. Clin Orthop Relat Res 1983;2:3–33. [11] Liddle D, Rome K, Howe T. Vertical ground reaction forces in patients with unilateral plantar heel pain – a pilot study. Gait Posture 2000;11:62–6. [12] Wearing SC, Smeathers JE, Sullivan PM, Yates B, Urry SR, Dubois P. Plantar fasciitis: are pain and fascial thickness associated with arch shape and loading. Phys Ther 2007;87:1002–8. [13] Ribeiro AP, Trombini-Souza F, Tessutti VD, Lima FR, Joao SM, Sacco IC. The effects of plantar fasciitis and pain on plantar pressure distribution of recreational runners. Clin Biomech (Bristol Avon) 2011;26:194–9. [14] Bedi HS, Love BR. Differences in impulse distribution in patients with plantar fasciitis. Foot Ankle Int/Am Orthop Foot Ankle Soc [and] Swiss Foot Ankle Soc 1998;19:153–6. [15] Bennett PJ, Patterson C, Wearing S, Baglioni T. Development and validation of a questionnaire designed to measure foot-health status. J Am Podiatr Med Assoc 1998;88:419–28. [16] Gurney JK, Kersting UG, Rosenbaum D. Between-day reliability of repeated plantar pressure distribution measurements in a normal population. Gait Posture 2008;27:706–9. [17] Bryant A, Singer K, Tinley P. Comparison of the reliability of plantar pressure measurements using the two-step and midgait methods of data collection. Foot Ankle Int/Am Orthop Foot Ankle Soc [and] Swiss Foot Ankle Soc 1999;20:646–50. [18] Wearing SC, Hennig EM, Byrne NM, Steele JR, Hills AP. Musculoskeletal disorders associated with obesity: a biomechanical perspective. Obes Rev 2006;7:239–50. [19] Peduzzi de Castro M, Abreu S, Pinto V, Santos R, Machado L, Vaz M, et al. Influence of pressure-relief insoles developed for loaded gait (backpackers and obese people) on plantar pressure distribution and ground reaction forces. Appl Ergon 2014;45:1028–34. [20] Fabris S, Valezi A, de Souza S, Faintuch J, Cecconello I, Junior M. Computerized baropodometry in obese patients. Obes Surg 2006;16:1574–8. [21] Menz HB, Morris ME. Clinical determinants of plantar forces and pressures during walking in older people. Gait Posture 2006;24:229–36. [22] Burns J, Crosbie J, Hunt A, Ouvrier R. The effect of pes cavus on foot pain and plantar pressure. Clin Biomech (Bristol Avon) 2005;20:877–82.
693
[23] Morag E, Cavanagh PR. Structural and functional predictors of regional peak pressures under the foot during walking. J Biomech 1999;32:359–70. [24] Scott G, Menz HB, Newcombe L. Age-related differences in foot structure and function. Gait Posture 2007;26:68–75. [25] Hills AP, Hennig EM, Byrne NM, Steele JR. The biomechanics of adiposity – structural and functional limitations of obesity and implications for movement. Obes Rev 2002;3:35–43. [26] Wearing SC, Smeathers JE, Urry SR, Sullivan PM, Yates B, Dubois P. Plantar enthesopathy: thickening of the enthesis is correlated with energy dissipation of the plantar fat pad during walking. Am J Sports Med 2010;38:2522–7. [27] Wearing SC, Smeathers JE, Yates B, Urry SR, Dubois P. Bulk compressive properties of the heel fat pad during walking: a pilot investigation in plantar heel pain. Clin Biomech 2009;24:397–402. [28] Hicks JH. The mechanics of the foot. II. The plantar aponeurosis and the arch. J Anat 1954;88:25–30. [29] Kappel-Bargas A, Woolf RD, Cornwall MW, McPoil TG. The windlass mechanism during normal walking and passive first metatarsalphalangeal joint extension. Clin Biomech 1998;13:190–4. [30] Erdemir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA. Dynamic loading of the plantar aponeurosis in walking. J Bone Jt Surg 2004;86:546–52. [31] Griffin NL, Miller CE, Schmitt D, D’Aout K. Understanding the evolution of the windlass mechanism of the human foot from comparative anatomy: insights, obstacles, and future directions. Am J Phys Anthropol 2015;156:1–10. [32] Cheng H-YK, Lin C-L, Wang H-W, Chou S-W. Finite element analysis of plantar fascia under stretch – the relative contribution of windlass mechanism and Achilles tendon force. J Biomech 2008;41:1937–44. [33] Chang R, Rodrigues PA, Van Emmerik RE, Hamill J. Multi-segment foot kinematics and ground reaction forces during gait of individuals with plantar fasciitis. J Biomech 2014;47:2571–7. [34] Katoh Y, Chao EY, Morrey BF, Laughman RK. Objective technique for evaluating painful heel syndrome and its treatment. Foot Ankle 1983;3:227–37. [35] Landorf KB, Menz HB. Plantar heel pain and fasciitis. Clin Evid 2008;2008. [36] Bonanno DR, Landorf KB, Menz HB. Pressure-relieving properties of various shoe inserts in older people with plantar heel pain. Gait Posture 2011;33:385–9. [37] Chia KK, Suresh S, Kuah A, Ong JL, Phua JM, Seah AL. Comparative trial of the foot pressure patterns between corrective orthotics, formthotics, bone spur pads and flat insoles in patients with chronic plantar fasciitis. Ann Acad Med Singapore 2009;38:869–75. [38] Richards J, Thewlis D. Measurement of force and pressure. In: Richards J, editor. Biomechanics in Clinic and Research. Edinburgh: Churchill Livingstone:Elsevier; 2008. p. 89–101. [39] Giacomozzi C, Keijsers N, Pataky T, Rosenbaum D. International scientific consensus on medical plantar pressure measurement devices: technical requirements and performance. Ann dell’Ist Super Sanita` 2012;48:259–71. [40] Butterworth PA, Landorf KB, Smith SE, Menz HB. The association between body mass index and musculoskeletal foot disorders: a systematic review. Obes Rev 2012;13:630–42. [41] Segal A, Rohr E, Orendurff M, Shofer J, O’Brien M, Sangeorzan B. The effect of walking speed on peak plantar pressure. Foot Ankle Int 2004;25:926–33.
