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Journal of Bodywork & Movement Therapies (2015) xx, 1e7
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/jbmt
ORIGINAL RESEARCH
Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain? ˜o Almeida, PT, MSc a,b,*, Gabriel Peixoto Lea Ana Paula de Moura Campos Carvalho e Silva, PT, MSc a, ´bio Jorge Renovato Franc Fa ¸a, PT, PhD a, ˜es, PT, MSc, PhD student a, Maurı´cio Oliveira Magalha Thomaz Nogueira Burke, PT, PhD a, ´lia Pasqual Marques, PT, PhD a Ame a Physical Therapy, Speech and Occupational Therapy Department, School of Medicine, University of Sa˜o Paulo, Sa˜o Paulo, SP, Brazil b Physical Therapy Department, Faculty of Medicine, Federal University of Ceara´, Fortaleza, CE, Brazil
Received 5 December 2014; received in revised form 19 January 2015; accepted 19 January 2015
KEYWORDS Anterior knee pain; Kinematic; Knee injuries; Patellofemoral joint; Muscle strength dynamometer
Summary The aim of the present study was to determine the relationship between knee pain severity and function with the frontal plane projection angle (FPPA) and trunk and hip peak torque (PT) in women with patellofemoral pain (PFPS). Twenty-two women with PFPS were assessed. Knee pain severity (KPS) was assessed with an 11-point visual analog scale and function with an Anterior Knee Pain Scale. The FPPA was recorded with a digital camera. PT of extensors, abductors, and the lateral rotators of hip and lateral core stability were measured with a handheld dynamometer. FPPA was the only predictor for the KPS. Regarding predictors of function, PT of lateral core stability and the extensor and abductor of the hip explained 41.4% of the function. Increase in FPPA was associated with greater KPS, and the lowest PT of lateral core stability, hip abductors, and extensors was associated with lower function in women with PFPS. ª 2015 Elsevier Ltd. All rights reserved.
* Corresponding author. Alexandre Barau ´filo, 60430-160; Ceara ´, CE, Brazil. Tel.: þ55 85 33668632. ´na Street, 949 e 1 andar e Rodolfo Teo E-mail address: [email protected] (G.P.L. Almeida). http://dx.doi.org/10.1016/j.jbmt.2015.01.004 1360-8592/ª 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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G.P.L. Almeida et al.
Introduction
Methods
Patellofemoral Pain Syndrome (PFPS) is characterized by anterior knee pain, with incidences 2.2 times higher in women than in men (Boling et al., 2010). Excessive pressure between the lateral side of the patella and the lateral femoral condyle appears to be associated with the syndrome’s development (Powers, 2010). However, the etiology of PFPS is unclear and various risk factors are cited in the literature (Cowan et al., 2001; Prins and van der Wurff, 2009). Kinematic studies (Powers, 2010; Souza et al., 2010) have pointed to difference of the patellofemoral joint in patients with PFPS during activities in open and closed kinetic chains. During weight-bearing activities, patellofemoral pain is more commonly referred in which excessive medial rotation and adduction of the femur occurs, increasing the compressive forces on the patellofemoral joint. Several researchers have verified strength deficit of the hip stabilizers (abductors, extensors and lateral rotators) in the women with PFPS (Prins and van der Wurff, 2009; Magalhaes et al., 2010). The deficit of these muscles can cause changes in control of the lower limb, causing higher peak internal rotation and adduction of the hip (Hewett et al., 2006; Souza and Powers, 2009a, 2009b; Willson and Davis, 2009). As the foot is fixed to the ground, the center of the knee joint moves medially relative to the hip and foot, resulting in a mechanism known as dynamic knee valgus (Powers, 2003; McLean et al., 2005; Willson and Davis, 2008; Powers, 2010). The analysis of dynamic knee valgus in 2D is known as the Frontal Plane Projection Angle (FPPA) (Willson and Davis, 2008). Studies (Long-Rossi and Salsich, 2010; Nakagawa et al., 2011, 2013) have proposed to evaluate the association between pain intensity, function, and the strength of the hip muscles. The eccentric peak torque of the external rotators and the strength of the hip abductors are associated with increased pain and decreased function in women with PFPS (Long-Rossi and Salsich, 2010; Nakagawa et al., 2011). Greater hip adduction and medial rotation and knee abduction are associated with higher levels of pain and reduced function of the knee in men and women with PFPS (Nakagawa et al., 2013). The greater FPPA and trunk and hip strength deficits have been reported in patients with PFPS (Cowan et al., 2009; Prins and van der Wurff, 2009). Although there are currently no studies that report on the relationship of anterior knee pain severity and function with the FPPA and trunk strength, and few studies that report on the strength of the hip muscles with these variables (Long-Rossi and Salsich, 2010; Nakagawa et al., 2011). Knowledge of factors that contribute to pain intensity and function in patients with PFPS may direct specific treatment strategies. Thus, the aim of this research was to determine if knee pain severity and function relate to the FPPA and trunk and hip strength in women with patellofemoral pain. Our hypothesis is that higher knee pain and lower levels of function are related to greater FPPA and lesser trunk and hip strength.
Subjects This cross-sectional study enrolled 22 women with patellofemoral pain ranging in age from 18 to 45 years. Men were excludes for gender differences influencing strength and kinematics and patellofemoral pain incidences 2.2 times higher in women (Boling et al., 2010). Individuals over the age of 45 years were excluded in order to minimize the effects of degenerative joint diseases (Souza and Powers, 2009a, 2009b). Women with patellofemoral pain participated in this study if their pain during the previous week had reached a minimum of 3 on an 11-point visual analog scale (VAS) (Bolgla et al., 2008). Pain had to be present during at least two of the following situations: ascending or descending stairs, squatting, kneeling, prolonged sitting, resisting isometric knee extension, jumping, running and performing lateral and/or medial palpation of the patella (Willson and Davis, 2008). They also had to report insidious onset of pain and pain for at least 3 months, and to demonstrate at least a 15-point deficit on the Anterior Knee Pain Scale (total score less than 86 out of 100 possible points) (Watson et al., 2005). Cases were excluded if they had previous knee, hip, ankle and/or spine surgery; patellar luxation; knee instability; meniscal, ligament, tendon, or cartilage injury; evidence of joint edema; body mass index greater than 28 Kg/ m2; limb length discrepancy greater than 2 cm; gait disturbances; history of low back pain for more than two consecutive weeks in the last six months and muscular or articular hip pain. All subjects were recruited from orthopedic clinics in the city of Fortaleza, as well as by use of flyers in the University campus. Subjects provided written informed consent and the present study was approved by the Research Ethics Committee of the University of Sa ˜o Paulo.
Procedure Anthropometric and clinical characteristics were assessed. Pain was assessed by use of an 11-point VAS, where 0 corresponded to no pain and 10 corresponded to worst imaginable pain. This scale has been validated and is reliable for assessing knee pain (Crossley et al., 2004). The function was assessed using Anterior Knee Pain Scale (AKPS), a 13item questionnaire (da Cunha et al., 2013). The highest possible score is 100, and higher scores reflect better function. The minimum clinically relevant score is 13 points (Watson et al., 2005).
Assessment of the frontal plane projection angle Kinematics of the knee during step-down was evaluated using 2D videos recorded with a digital camera (Sony Cybershot DSC-W35). Nakagawa et al. (2013) investigated the relationship of hip and knee kinematic variables in 3D and found that both peak internal hip rotation and adduction and knee abduction are predictors of pain.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Does anterior knee pain severity and function relate to the frontal plane projection angle? Three adhesive markers were placed on the midpoint of the ankle malleoli, on the midpoint of the femoral condyles, and on the proximal thigh along a line from the ASIS to approximately 30 cm above the knee marker (Fig. 1) (Willson and Davis, 2008). The height of the step was customized as 10% of the subject’s height (Souza and Powers, 2009a, 2009b). One foot was positioned over a standard reference line, and the contralateral heel touch point was 5 cm away from the step. The digital camera was positioned 2 m ahead of the subject, perpendicular to the frontal plane and at the height of the knee joint in singleleg stance. Subjects received verbal instructions on the performance of step-down without specific directions on knee and hip alignment. After that, they performed practice trials, followed by a 60 s interval before the performance trials (Olson et al., 2010). Each step-down was to be completed over 5 s intervals from descending to ascending, paced by a digital chronometer. Upright standing participants (1s) were instructed to perform the step-down until the suspended heel contacted the ground (3s), and then to return to the standing position (5s). A digital picture was taken as the suspended heel contacted the ground. Image sequences were captured using VirtualDub software (Copyright Avery Lee 1998e2009). FPPA measurements were calculated using the Postural Assessment Software (SAPO) v.0.68, which measures distances and angles (Ferreira et al., 2010). FPPAs were measured at the end of step-down (Fig. 1) (Willson and Davis, 2008). The average of five tests of each inferior limb was accepted for analysis (Willson and Davis, 2008).
Figure 1
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Isometric muscular strength assessment A Nicholas handheld dynamometer (Lafayette Instrument Company, Lafayette, Indiana, EUA) was used to measure strength. This method has good to excellent interrater and intrarater reliability for measurements of hip strength in women with PFPS (Piva et al., 2005; Robinson and Nee, 2007). To mitigate the influence of the examiner, a strap was used for all tests. Participants were instructed to push the dynamometer as hard as they could for 5 s. They performed one practice trial, rested for 30 s and then performed the measured trials. Three tests were performed, with 30 s between each trial. Mean values were calculated for each participant. Before changing muscular group, participants rested for 1 min. When compensation was identified, values were discarded, with a new evaluation after 20 s. Force data were converted to torque (Nm) and normalized to body mass: (Torque [Nm] O Weight [kg]) 100. Participants were positioned as previously reported (Souza and Powers, 2009a, 2009b). The sequence of assessments was randomized by use of the Random Allocation Software (v. 1.0.0). Isometric hip abductor torque was measured with participants in lateral decubitus, with lower hip and knee positioned at 45 of flexion. The limb was abducted (20 ), discretely extended (10 ), neutral for hip rotation and with extended knee. The dynamometer was positioned 5 cm proximal to the lateral malleolus midpoint. The moment arm was the distance from the greater trochanter to the dynamometer center.
Frontal plane projection angle (FPPA) during a step-down. A) Dynamic knee valgus, B) Without dynamic knee valgus.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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4 Isometric hip extensor torque was measured with subjects in prone position. The limb that was not being assessed was fully extended, while the assessed limb was in 10 of extension, with light hip external rotation and 90 of knee flexion. The dynamometer was positioned over the posterior thigh, 5 cm proximal to the popliteal crease. The moment arm was the distance from the ischial tuberosity to the dynamometer center. Isometric hip external rotator torque was tested with participants in the sitting position, with hip and knees flexed to 90 . The dynamometer was positioned over the distal-medial tibia, 5 cm proximal to the medial malleolus midpoint. Straps were used to prevent subjects from adducting the hip. The moment arm was the distance from the lateral femoral condyle to the dynamometer center. Isometric lateral core stability test was tested with participants lay on one side supported by the elbow and, with their opposite hand on their shoulder, the dynamometer was placed just proximal to the greater trochanter (Willson et al., 2006). The moment arm was the distance from the lateral malleolus to the dynamometer center.
Statistical analysis Descriptive analysis (mean and standard deviation) was obtained for all variables. Initially, the ShapiroeWilk test was used to determine the normative variance of the data. A correlation matrix of the Pearson product-moment was used to evaluate the correlation between the dependent variables (pain intensity and function) and independent variables (FPPA knee, peak torque of hip abductors, external rotators, extensors, and lateral core stability). The r values were interpreted as follows: 0e.19 Z none to slight, .2e.39 Z low, .4e.69 Z modest, .7e.89 Z high, and .9e1 Z very high [27](Weber and Lamb, 1970). Only variables that were initially significantly correlated with dependent variables were subsequently considered in the logistic regression model (P < .05). Hierarchical linear regression analysis was used to investigate associations between dependent and independents variables. Variables with p-values less than .10 in the univariate analysis were included in the multivariate regression analysis, higher correlations were included first (Mickey and Greenland, 1989). For multivariate regression, the analysis assumed a significance level of 5%. For all statistical analyses, we used the SPSS 17.0 software for Windows (Statistical Package for the Social Sciences Inc., Chicago, IL, USA).
Results The demographic and clinical characteristics are shown in Table 1. The FPPA showed a moderate positive correlation with the severity of pain in women with PFPS (r Z .55; P Z .008) (Table 2). Function showed a moderate positive correlation with the peak torque of the hip abductors (r Z .46; P Z .03), hip extensors (r Z .49; P Z .02), and lateral core stability (r Z .63; P Z .002) (Table 2). In the multiple regression model, FPPA knee was a predictor for the severity of knee pain (r2 Z .31; P Z .008), with 30.6% of patellofemoral pain attributed to this
G.P.L. Almeida et al. Table 1 Baseline (Mean SD) characteristics of the women with patellofemoral pain syndrome.
Age (years) Weight (Kg) Height (m) BMI (Kg/m2) Duration of pain (month) VAS (0e10) AKPS (0e100) FPPA (degrees) Abduction (N.m/kg) Extension (N.m/kg) External rotation (N.m/kg) Trunk side flexion (N.m/kg)
Median
SD
28.1 59.9 1.63 22.4 22.1 5.8 71 11.9 75.5 43.9 35.1 181.9
9.3 7 .07 2.6 16.5 1.8 10.1 5.9 24.6 22.3 9.3 89.2
Abbreviations: BMI. Body Mass Index; VAS, Visual Analog Scale for Pain; AKPS, Anterior Knee Pain Scale; FPPA, Frontal Plane Projection Angle.
Table 2 Pearson correlation coefficient (r) between the dependent variables (pain and functional capacity) and independent variables (FPPA, strength of hip and trunk muscles).
Abduction Extension External rotation Trunk side flexion FPPA
Pain severity
Functional capacity
.04 .11 .08 .07 .55b
.46a .49a .35 .63b .19
Abbreviations: FPPA, Frontal Plane Projection Angle. a Statistical significance (P < .05). b Statistical significance (P < .01).
variable (Table 3). With regard to the variables predicting function in women with PFPS, the peak torque of the lateral core stability explains 40.0% (r2 Z .40; P Z .002), of the hip extensor 23.5% (r2 Z .23; P Z .02), and of the hip abductor 21.1% (r2 Z .21; P Z .03) of the overall variance. Together, lateral core stability, hip extensor and hip abductor
Table 3 Multiple regression model of the association of independent variables with pain intensity and functional capacity. R2 Pain Severity 1 FPPA Functional Capacity 1 Trunk side flexion 2 Trunk side flexion Extension 3 Trunk side flexion Extension Abduction
F
P-Value
.31
8.82
.008
.40 .41
13.34 6.63
.002 .007
.41
4.23
.02
Abbreviations: FPPA, Frontal Plane Projection Angle.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Does anterior knee pain severity and function relate to the frontal plane projection angle? explained 41.4% of the function of the knee in women with PFPS (r2 Z .41; P Z .02) (Table 3).
Discussion The aim of this study was to investigate the relationship between anterior knee pain severity and function with the FPPA and core and hip strength in women with patellofemoral pain. Our initial hypothesis was partially confirmed. The FPPA was positively correlated with the intensity of pain in women with PFPS. There was no correlation with function, yet the peak torque of the lateral core stability, hip abductors, and extensors showed significant a positive correlation with function. The FPPA was the best predictor of anterior knee pain severity in women with PFPS. Evaluation of knee kinematics through FPPA has been previously established via imaging techniques in 3D (McLean et al., 2005; Willson and Davis, 2008), and studies indicate excessive FPPA in women with PFPS compared to women without pain (Levinger et al., 2007; Willson and Davis, 2008). Two-dimensional images require simpler, portable and lower cost equipment, which facilitates their use happen in the clinical environment. Noehren et al. (2013) and Boling et al. (2009) verified in prospective studies that greater hip adduction and internal rotation were a risk factor for the development of PFPS. Increased FPPA creates a lateral force vector patellar, increasing compressive loads on the lateral side of the patella and the lateral femoral condyle (Powers, 2010; Souza et al., 2010). An increase in the q-angle of 10 can increase patellofemoral stress by 45% (Huberti and Hayes, 1984). Recent studies have shown the relationship between the hip stabilizing muscles, extensors, abductors, and external rotators and the development of patellofemoral pain. A systematic review published by Prins and van der Wurff (2009) reports that women with PFPS exhibit decreased strength of the abductor muscles, external rotators, and hip extensors compared to asymptomatic controls. The results of our study found that the peak torque of the lateral core stability, hip abductors, and extensors were positively correlated with function, explaining 41% of the variance in knee function. Corroborating these results, Long-Rossi and Salsich (2010) and Nakagawa et al. (2011) each found a relationship between the strength of the hip muscles and function in women with PFPS. However, no correlation was found between the peak torque of the hip and trunk muscles and pain intensity. The literature in this respect differs. Nakagawa et al. (2011) found this relationship, while two other studies did not (Piva et al., 2009; Long-Rossi and Salsich, 2010). These results support the use of hip strengthening exercises to improve function in women with PFPS. The strengthening of the hip muscles, mainly targeting the extensors, abductors, and external rotators, is widely used for the correction of dynamic knee valgus, decreased peak adduction, and internal rotation of the hip (Herman et al., 2009; Snyder et al., 2009; Greska et al., 2012). The stabilization of the lumbarepelvic complex is formed by deep stabilizing muscles (local) and surface muscles (global) known in the literature together as the core. Core stability is defined as the ability to control the
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trunk in response to internal and external disturbances, anticipated or not, in the production, transfer, and control of forces and motion of the distal segment kinetic chain (Kibler et al., 2006). The stability and neuromuscular control of the complex lumbo-pelvic-hip are associated with lower risk of knee injuries, especially in women (Leetun et al., 2004; Myer et al., 2008). Our study found the isometric peak torque of the lateral core stability to be the best predictor of function in women with PFPS. Core stability is the result of the muscular capacity of the complex lumbo-pelvic-hip, in that the strength of the hip evaluates only one element of that complex (Leetun et al., 2004). Willson and Davis (2009), Willson et al. (2008) and Cowan et al. (2009) reported a 24e29% deficit between the lateral core stability in individuals with SDP compared to controls.
Limitations The results of this study add to scientific information on the relationship between dynamic knee valgus and anterior knee pain severity, as well as the relationship between function and hip and trunk strength in women with PFPS. However, it is important to note that less than half of the variance in pain intensity and function was explained by FPPA and the torque of the hip and trunk muscles, respectively. This demonstrates that, due to the multifactorial nature of PFPS, other possible anatomical, biomechanical, neuromuscular, and psychological factors that were not studied may have contributed to the variance in pain intensity and functional impairment. Thus, future research should add other variables related to the development of PFPS to verify their influence on the severity of pain and functional impairment. Moreover, due to the transverse nature of this study, it could not establish a cause-and-effect relationship between the variables.
Conclusion The results of this study demonstrate that greater frontal plane projection angle (dynamic knee valgus) are associated with greater anterior knee pain severity in women with PFPS. The lower peak torque of lateral core stability, hip abductors, and extensors were associated with reduced function in women with PFPS. It is suggested that the improvement of the dynamic knee valgus and torque of the hip and trunk stabilizers should be considered in planning treatment strategies for patients with PFPS to reduce pain and improve function of the knee.
Ethical approval Ethical Committee of University of Sa ˜o Paulo number: 120/12.
Acknowledgments This study had Public Financial Support, #2012/10768-0 Sa ˜o Paulo Research Foundation (FAPESP).
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Does anterior knee pain severity and function relate to the frontal plane projection angle? Willson, J.D., Binder-Macleod, S., Davis, I.S., 2008. Lower extremity jumping mechanics of female athletes with and without patellofemoral pain before and after exertion. Am. J. Sports Med. 36, 1587e1596. Willson, J.D., Davis, I.S., 2008. Utility of the frontal plane projection angle in females with patellofemoral pain. J. Orthop. Sports Phys. Ther. 38, 606e615.
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Willson, J.D., Davis, I.S., 2009. Lower extremity strength and mechanics during jumping in women with patellofemoral pain. J. Sport Rehabil. 18, 76e90. Willson, J.D., Ireland, M.L., Davis, I., 2006. Core strength and lower extremity alignment during single leg squats. Med. Sci. Sports Exerc 38, 945e952.
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Journal of Bodywork & Movement Therapies (2015) xx, 1e7
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ORIGINAL RESEARCH
Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain? ˜o Almeida, PT, MSc a,b,*, Gabriel Peixoto Lea Ana Paula de Moura Campos Carvalho e Silva, PT, MSc a, ´bio Jorge Renovato Franc Fa ¸a, PT, PhD a, ˜es, PT, MSc, PhD student a, Maurı´cio Oliveira Magalha Thomaz Nogueira Burke, PT, PhD a, ´lia Pasqual Marques, PT, PhD a Ame a Physical Therapy, Speech and Occupational Therapy Department, School of Medicine, University of Sa˜o Paulo, Sa˜o Paulo, SP, Brazil b Physical Therapy Department, Faculty of Medicine, Federal University of Ceara´, Fortaleza, CE, Brazil
Received 5 December 2014; received in revised form 19 January 2015; accepted 19 January 2015
KEYWORDS Anterior knee pain; Kinematic; Knee injuries; Patellofemoral joint; Muscle strength dynamometer
Summary The aim of the present study was to determine the relationship between knee pain severity and function with the frontal plane projection angle (FPPA) and trunk and hip peak torque (PT) in women with patellofemoral pain (PFPS). Twenty-two women with PFPS were assessed. Knee pain severity (KPS) was assessed with an 11-point visual analog scale and function with an Anterior Knee Pain Scale. The FPPA was recorded with a digital camera. PT of extensors, abductors, and the lateral rotators of hip and lateral core stability were measured with a handheld dynamometer. FPPA was the only predictor for the KPS. Regarding predictors of function, PT of lateral core stability and the extensor and abductor of the hip explained 41.4% of the function. Increase in FPPA was associated with greater KPS, and the lowest PT of lateral core stability, hip abductors, and extensors was associated with lower function in women with PFPS. ª 2015 Elsevier Ltd. All rights reserved.
* Corresponding author. Alexandre Barau ´filo, 60430-160; Ceara ´, CE, Brazil. Tel.: þ55 85 33668632. ´na Street, 949 e 1 andar e Rodolfo Teo E-mail address: [email protected] (G.P.L. Almeida). http://dx.doi.org/10.1016/j.jbmt.2015.01.004 1360-8592/ª 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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G.P.L. Almeida et al.
Introduction
Methods
Patellofemoral Pain Syndrome (PFPS) is characterized by anterior knee pain, with incidences 2.2 times higher in women than in men (Boling et al., 2010). Excessive pressure between the lateral side of the patella and the lateral femoral condyle appears to be associated with the syndrome’s development (Powers, 2010). However, the etiology of PFPS is unclear and various risk factors are cited in the literature (Cowan et al., 2001; Prins and van der Wurff, 2009). Kinematic studies (Powers, 2010; Souza et al., 2010) have pointed to difference of the patellofemoral joint in patients with PFPS during activities in open and closed kinetic chains. During weight-bearing activities, patellofemoral pain is more commonly referred in which excessive medial rotation and adduction of the femur occurs, increasing the compressive forces on the patellofemoral joint. Several researchers have verified strength deficit of the hip stabilizers (abductors, extensors and lateral rotators) in the women with PFPS (Prins and van der Wurff, 2009; Magalhaes et al., 2010). The deficit of these muscles can cause changes in control of the lower limb, causing higher peak internal rotation and adduction of the hip (Hewett et al., 2006; Souza and Powers, 2009a, 2009b; Willson and Davis, 2009). As the foot is fixed to the ground, the center of the knee joint moves medially relative to the hip and foot, resulting in a mechanism known as dynamic knee valgus (Powers, 2003; McLean et al., 2005; Willson and Davis, 2008; Powers, 2010). The analysis of dynamic knee valgus in 2D is known as the Frontal Plane Projection Angle (FPPA) (Willson and Davis, 2008). Studies (Long-Rossi and Salsich, 2010; Nakagawa et al., 2011, 2013) have proposed to evaluate the association between pain intensity, function, and the strength of the hip muscles. The eccentric peak torque of the external rotators and the strength of the hip abductors are associated with increased pain and decreased function in women with PFPS (Long-Rossi and Salsich, 2010; Nakagawa et al., 2011). Greater hip adduction and medial rotation and knee abduction are associated with higher levels of pain and reduced function of the knee in men and women with PFPS (Nakagawa et al., 2013). The greater FPPA and trunk and hip strength deficits have been reported in patients with PFPS (Cowan et al., 2009; Prins and van der Wurff, 2009). Although there are currently no studies that report on the relationship of anterior knee pain severity and function with the FPPA and trunk strength, and few studies that report on the strength of the hip muscles with these variables (Long-Rossi and Salsich, 2010; Nakagawa et al., 2011). Knowledge of factors that contribute to pain intensity and function in patients with PFPS may direct specific treatment strategies. Thus, the aim of this research was to determine if knee pain severity and function relate to the FPPA and trunk and hip strength in women with patellofemoral pain. Our hypothesis is that higher knee pain and lower levels of function are related to greater FPPA and lesser trunk and hip strength.
Subjects This cross-sectional study enrolled 22 women with patellofemoral pain ranging in age from 18 to 45 years. Men were excludes for gender differences influencing strength and kinematics and patellofemoral pain incidences 2.2 times higher in women (Boling et al., 2010). Individuals over the age of 45 years were excluded in order to minimize the effects of degenerative joint diseases (Souza and Powers, 2009a, 2009b). Women with patellofemoral pain participated in this study if their pain during the previous week had reached a minimum of 3 on an 11-point visual analog scale (VAS) (Bolgla et al., 2008). Pain had to be present during at least two of the following situations: ascending or descending stairs, squatting, kneeling, prolonged sitting, resisting isometric knee extension, jumping, running and performing lateral and/or medial palpation of the patella (Willson and Davis, 2008). They also had to report insidious onset of pain and pain for at least 3 months, and to demonstrate at least a 15-point deficit on the Anterior Knee Pain Scale (total score less than 86 out of 100 possible points) (Watson et al., 2005). Cases were excluded if they had previous knee, hip, ankle and/or spine surgery; patellar luxation; knee instability; meniscal, ligament, tendon, or cartilage injury; evidence of joint edema; body mass index greater than 28 Kg/ m2; limb length discrepancy greater than 2 cm; gait disturbances; history of low back pain for more than two consecutive weeks in the last six months and muscular or articular hip pain. All subjects were recruited from orthopedic clinics in the city of Fortaleza, as well as by use of flyers in the University campus. Subjects provided written informed consent and the present study was approved by the Research Ethics Committee of the University of Sa ˜o Paulo.
Procedure Anthropometric and clinical characteristics were assessed. Pain was assessed by use of an 11-point VAS, where 0 corresponded to no pain and 10 corresponded to worst imaginable pain. This scale has been validated and is reliable for assessing knee pain (Crossley et al., 2004). The function was assessed using Anterior Knee Pain Scale (AKPS), a 13item questionnaire (da Cunha et al., 2013). The highest possible score is 100, and higher scores reflect better function. The minimum clinically relevant score is 13 points (Watson et al., 2005).
Assessment of the frontal plane projection angle Kinematics of the knee during step-down was evaluated using 2D videos recorded with a digital camera (Sony Cybershot DSC-W35). Nakagawa et al. (2013) investigated the relationship of hip and knee kinematic variables in 3D and found that both peak internal hip rotation and adduction and knee abduction are predictors of pain.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Does anterior knee pain severity and function relate to the frontal plane projection angle? Three adhesive markers were placed on the midpoint of the ankle malleoli, on the midpoint of the femoral condyles, and on the proximal thigh along a line from the ASIS to approximately 30 cm above the knee marker (Fig. 1) (Willson and Davis, 2008). The height of the step was customized as 10% of the subject’s height (Souza and Powers, 2009a, 2009b). One foot was positioned over a standard reference line, and the contralateral heel touch point was 5 cm away from the step. The digital camera was positioned 2 m ahead of the subject, perpendicular to the frontal plane and at the height of the knee joint in singleleg stance. Subjects received verbal instructions on the performance of step-down without specific directions on knee and hip alignment. After that, they performed practice trials, followed by a 60 s interval before the performance trials (Olson et al., 2010). Each step-down was to be completed over 5 s intervals from descending to ascending, paced by a digital chronometer. Upright standing participants (1s) were instructed to perform the step-down until the suspended heel contacted the ground (3s), and then to return to the standing position (5s). A digital picture was taken as the suspended heel contacted the ground. Image sequences were captured using VirtualDub software (Copyright Avery Lee 1998e2009). FPPA measurements were calculated using the Postural Assessment Software (SAPO) v.0.68, which measures distances and angles (Ferreira et al., 2010). FPPAs were measured at the end of step-down (Fig. 1) (Willson and Davis, 2008). The average of five tests of each inferior limb was accepted for analysis (Willson and Davis, 2008).
Figure 1
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Isometric muscular strength assessment A Nicholas handheld dynamometer (Lafayette Instrument Company, Lafayette, Indiana, EUA) was used to measure strength. This method has good to excellent interrater and intrarater reliability for measurements of hip strength in women with PFPS (Piva et al., 2005; Robinson and Nee, 2007). To mitigate the influence of the examiner, a strap was used for all tests. Participants were instructed to push the dynamometer as hard as they could for 5 s. They performed one practice trial, rested for 30 s and then performed the measured trials. Three tests were performed, with 30 s between each trial. Mean values were calculated for each participant. Before changing muscular group, participants rested for 1 min. When compensation was identified, values were discarded, with a new evaluation after 20 s. Force data were converted to torque (Nm) and normalized to body mass: (Torque [Nm] O Weight [kg]) 100. Participants were positioned as previously reported (Souza and Powers, 2009a, 2009b). The sequence of assessments was randomized by use of the Random Allocation Software (v. 1.0.0). Isometric hip abductor torque was measured with participants in lateral decubitus, with lower hip and knee positioned at 45 of flexion. The limb was abducted (20 ), discretely extended (10 ), neutral for hip rotation and with extended knee. The dynamometer was positioned 5 cm proximal to the lateral malleolus midpoint. The moment arm was the distance from the greater trochanter to the dynamometer center.
Frontal plane projection angle (FPPA) during a step-down. A) Dynamic knee valgus, B) Without dynamic knee valgus.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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4 Isometric hip extensor torque was measured with subjects in prone position. The limb that was not being assessed was fully extended, while the assessed limb was in 10 of extension, with light hip external rotation and 90 of knee flexion. The dynamometer was positioned over the posterior thigh, 5 cm proximal to the popliteal crease. The moment arm was the distance from the ischial tuberosity to the dynamometer center. Isometric hip external rotator torque was tested with participants in the sitting position, with hip and knees flexed to 90 . The dynamometer was positioned over the distal-medial tibia, 5 cm proximal to the medial malleolus midpoint. Straps were used to prevent subjects from adducting the hip. The moment arm was the distance from the lateral femoral condyle to the dynamometer center. Isometric lateral core stability test was tested with participants lay on one side supported by the elbow and, with their opposite hand on their shoulder, the dynamometer was placed just proximal to the greater trochanter (Willson et al., 2006). The moment arm was the distance from the lateral malleolus to the dynamometer center.
Statistical analysis Descriptive analysis (mean and standard deviation) was obtained for all variables. Initially, the ShapiroeWilk test was used to determine the normative variance of the data. A correlation matrix of the Pearson product-moment was used to evaluate the correlation between the dependent variables (pain intensity and function) and independent variables (FPPA knee, peak torque of hip abductors, external rotators, extensors, and lateral core stability). The r values were interpreted as follows: 0e.19 Z none to slight, .2e.39 Z low, .4e.69 Z modest, .7e.89 Z high, and .9e1 Z very high [27](Weber and Lamb, 1970). Only variables that were initially significantly correlated with dependent variables were subsequently considered in the logistic regression model (P < .05). Hierarchical linear regression analysis was used to investigate associations between dependent and independents variables. Variables with p-values less than .10 in the univariate analysis were included in the multivariate regression analysis, higher correlations were included first (Mickey and Greenland, 1989). For multivariate regression, the analysis assumed a significance level of 5%. For all statistical analyses, we used the SPSS 17.0 software for Windows (Statistical Package for the Social Sciences Inc., Chicago, IL, USA).
Results The demographic and clinical characteristics are shown in Table 1. The FPPA showed a moderate positive correlation with the severity of pain in women with PFPS (r Z .55; P Z .008) (Table 2). Function showed a moderate positive correlation with the peak torque of the hip abductors (r Z .46; P Z .03), hip extensors (r Z .49; P Z .02), and lateral core stability (r Z .63; P Z .002) (Table 2). In the multiple regression model, FPPA knee was a predictor for the severity of knee pain (r2 Z .31; P Z .008), with 30.6% of patellofemoral pain attributed to this
G.P.L. Almeida et al. Table 1 Baseline (Mean SD) characteristics of the women with patellofemoral pain syndrome.
Age (years) Weight (Kg) Height (m) BMI (Kg/m2) Duration of pain (month) VAS (0e10) AKPS (0e100) FPPA (degrees) Abduction (N.m/kg) Extension (N.m/kg) External rotation (N.m/kg) Trunk side flexion (N.m/kg)
Median
SD
28.1 59.9 1.63 22.4 22.1 5.8 71 11.9 75.5 43.9 35.1 181.9
9.3 7 .07 2.6 16.5 1.8 10.1 5.9 24.6 22.3 9.3 89.2
Abbreviations: BMI. Body Mass Index; VAS, Visual Analog Scale for Pain; AKPS, Anterior Knee Pain Scale; FPPA, Frontal Plane Projection Angle.
Table 2 Pearson correlation coefficient (r) between the dependent variables (pain and functional capacity) and independent variables (FPPA, strength of hip and trunk muscles).
Abduction Extension External rotation Trunk side flexion FPPA
Pain severity
Functional capacity
.04 .11 .08 .07 .55b
.46a .49a .35 .63b .19
Abbreviations: FPPA, Frontal Plane Projection Angle. a Statistical significance (P < .05). b Statistical significance (P < .01).
variable (Table 3). With regard to the variables predicting function in women with PFPS, the peak torque of the lateral core stability explains 40.0% (r2 Z .40; P Z .002), of the hip extensor 23.5% (r2 Z .23; P Z .02), and of the hip abductor 21.1% (r2 Z .21; P Z .03) of the overall variance. Together, lateral core stability, hip extensor and hip abductor
Table 3 Multiple regression model of the association of independent variables with pain intensity and functional capacity. R2 Pain Severity 1 FPPA Functional Capacity 1 Trunk side flexion 2 Trunk side flexion Extension 3 Trunk side flexion Extension Abduction
F
P-Value
.31
8.82
.008
.40 .41
13.34 6.63
.002 .007
.41
4.23
.02
Abbreviations: FPPA, Frontal Plane Projection Angle.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Does anterior knee pain severity and function relate to the frontal plane projection angle? explained 41.4% of the function of the knee in women with PFPS (r2 Z .41; P Z .02) (Table 3).
Discussion The aim of this study was to investigate the relationship between anterior knee pain severity and function with the FPPA and core and hip strength in women with patellofemoral pain. Our initial hypothesis was partially confirmed. The FPPA was positively correlated with the intensity of pain in women with PFPS. There was no correlation with function, yet the peak torque of the lateral core stability, hip abductors, and extensors showed significant a positive correlation with function. The FPPA was the best predictor of anterior knee pain severity in women with PFPS. Evaluation of knee kinematics through FPPA has been previously established via imaging techniques in 3D (McLean et al., 2005; Willson and Davis, 2008), and studies indicate excessive FPPA in women with PFPS compared to women without pain (Levinger et al., 2007; Willson and Davis, 2008). Two-dimensional images require simpler, portable and lower cost equipment, which facilitates their use happen in the clinical environment. Noehren et al. (2013) and Boling et al. (2009) verified in prospective studies that greater hip adduction and internal rotation were a risk factor for the development of PFPS. Increased FPPA creates a lateral force vector patellar, increasing compressive loads on the lateral side of the patella and the lateral femoral condyle (Powers, 2010; Souza et al., 2010). An increase in the q-angle of 10 can increase patellofemoral stress by 45% (Huberti and Hayes, 1984). Recent studies have shown the relationship between the hip stabilizing muscles, extensors, abductors, and external rotators and the development of patellofemoral pain. A systematic review published by Prins and van der Wurff (2009) reports that women with PFPS exhibit decreased strength of the abductor muscles, external rotators, and hip extensors compared to asymptomatic controls. The results of our study found that the peak torque of the lateral core stability, hip abductors, and extensors were positively correlated with function, explaining 41% of the variance in knee function. Corroborating these results, Long-Rossi and Salsich (2010) and Nakagawa et al. (2011) each found a relationship between the strength of the hip muscles and function in women with PFPS. However, no correlation was found between the peak torque of the hip and trunk muscles and pain intensity. The literature in this respect differs. Nakagawa et al. (2011) found this relationship, while two other studies did not (Piva et al., 2009; Long-Rossi and Salsich, 2010). These results support the use of hip strengthening exercises to improve function in women with PFPS. The strengthening of the hip muscles, mainly targeting the extensors, abductors, and external rotators, is widely used for the correction of dynamic knee valgus, decreased peak adduction, and internal rotation of the hip (Herman et al., 2009; Snyder et al., 2009; Greska et al., 2012). The stabilization of the lumbarepelvic complex is formed by deep stabilizing muscles (local) and surface muscles (global) known in the literature together as the core. Core stability is defined as the ability to control the
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trunk in response to internal and external disturbances, anticipated or not, in the production, transfer, and control of forces and motion of the distal segment kinetic chain (Kibler et al., 2006). The stability and neuromuscular control of the complex lumbo-pelvic-hip are associated with lower risk of knee injuries, especially in women (Leetun et al., 2004; Myer et al., 2008). Our study found the isometric peak torque of the lateral core stability to be the best predictor of function in women with PFPS. Core stability is the result of the muscular capacity of the complex lumbo-pelvic-hip, in that the strength of the hip evaluates only one element of that complex (Leetun et al., 2004). Willson and Davis (2009), Willson et al. (2008) and Cowan et al. (2009) reported a 24e29% deficit between the lateral core stability in individuals with SDP compared to controls.
Limitations The results of this study add to scientific information on the relationship between dynamic knee valgus and anterior knee pain severity, as well as the relationship between function and hip and trunk strength in women with PFPS. However, it is important to note that less than half of the variance in pain intensity and function was explained by FPPA and the torque of the hip and trunk muscles, respectively. This demonstrates that, due to the multifactorial nature of PFPS, other possible anatomical, biomechanical, neuromuscular, and psychological factors that were not studied may have contributed to the variance in pain intensity and functional impairment. Thus, future research should add other variables related to the development of PFPS to verify their influence on the severity of pain and functional impairment. Moreover, due to the transverse nature of this study, it could not establish a cause-and-effect relationship between the variables.
Conclusion The results of this study demonstrate that greater frontal plane projection angle (dynamic knee valgus) are associated with greater anterior knee pain severity in women with PFPS. The lower peak torque of lateral core stability, hip abductors, and extensors were associated with reduced function in women with PFPS. It is suggested that the improvement of the dynamic knee valgus and torque of the hip and trunk stabilizers should be considered in planning treatment strategies for patients with PFPS to reduce pain and improve function of the knee.
Ethical approval Ethical Committee of University of Sa ˜o Paulo number: 120/12.
Acknowledgments This study had Public Financial Support, #2012/10768-0 Sa ˜o Paulo Research Foundation (FAPESP).
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
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Does anterior knee pain severity and function relate to the frontal plane projection angle? Willson, J.D., Binder-Macleod, S., Davis, I.S., 2008. Lower extremity jumping mechanics of female athletes with and without patellofemoral pain before and after exertion. Am. J. Sports Med. 36, 1587e1596. Willson, J.D., Davis, I.S., 2008. Utility of the frontal plane projection angle in females with patellofemoral pain. J. Orthop. Sports Phys. Ther. 38, 606e615.
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Willson, J.D., Davis, I.S., 2009. Lower extremity strength and mechanics during jumping in women with patellofemoral pain. J. Sport Rehabil. 18, 76e90. Willson, J.D., Ireland, M.L., Davis, I., 2006. Core strength and lower extremity alignment during single leg squats. Med. Sci. Sports Exerc 38, 945e952.
Please cite this article in press as: Almeida, G.P.L., et al., Does anterior knee pain severity and function relate to the frontal plane projection angle and trunk and hip strength in women with patellofemoral pain?, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.01.004
