Arch Orthop Trauma Surg (2015) 135:1217–1226 DOI 10.1007/s00402-015-2276-9

ORTHOPAEDIC SURGERY

Pelvic movement strategies and leg extension power in patients with end-stage medial compartment knee osteoarthritis: a cross-sectional study Signe Kierkegaard1,2 • Peter Bo Jørgensen1 • Ulrik Dalgas3 • Kjeld Søballe1 Inger Mechlenburg1,4

•

Received: 16 January 2015 / Published online: 4 July 2015 Ó Springer-Verlag Berlin Heidelberg 2015

Abstract Introduction During movement tasks, patients with medial compartment knee osteoarthritis use compensatory strategies to minimise the joint load of the affected leg. Movement strategies of the knees and trunk have been investigated, but less is known about movement strategies of the pelvis during advancing functional tasks, and how these strategies are associated with leg extension power. The aim of the study was to investigate pelvic movement strategies and leg extension power in patients with endstage medial compartment knee osteoarthritis compared with controls. Materials and methods 57 patients (mean age 65.6 years) scheduled for medial uni-compartmental knee arthroplasty, and 29 age and gender matched controls were included in this cross-sectional study. Leg extension power was tested with the Nottingham Leg Extension Power-Rig. Pelvic

range of motion was derived from an inertia-based measurement unit placed over the sacrum bone during walking, stair climbing and stepping. Results Patients had lower leg extension power than controls (20–39 %, P \ 0.01) and used greater pelvic range of motion during stair and step ascending and descending (P B 0.03, except for pelvic range of motion in the frontal plane during ascending, P [ 0.06). Furthermore, an inverse association (coefficient: -0.03 to -0.04; R2 = 13–22 %) between leg extension power and pelvic range of motion during stair and step descending was found in the patients. Conclusions Compared to controls, patients with medial compartment knee osteoarthritis use greater pelvic movements during advanced functional performance tests, particularly when these involve descending tasks. Further studies should investigate if it is possible to alter these movement strategies by an intervention aimed at increasing strength and power for the patients.

Abstract presented orally at the Danish Orthopedic Society Congress, Copenhagen, Denmark, October 2014.

Keywords Knee osteoarthritis
Movement strategies
Pelvic movements
Leg extension power
Walking
Stair climbing

& Signe Kierkegaard [email protected] 1

Orthopaedic Research, Aarhus University Hospital, Building 10A, Office 5, Tage Hansens Gade 2, 8000 Aarhus C, Denmark

2

Department of Orthopaedic Surgery, Horsens Regional Hospital, Sundvej 30, 8700 Horsens, Denmark

3

Section of Sports Science, Department of Public Health, Aarhus University, Dalgas Avenue 4, 8000 Aarhus C, Denmark

4

Centre of Research in Rehabilitation (CORIR), Department of Clinical Medicine, Aarhus University Hospital and Aarhus University, Aarhus C, Denmark

Introduction Knee osteoarthritis (OA) is a disabling disease yearly resulting in 200–300 joint replacements per 100,000 individuals [1]. Furthermore, persons with knee OA have an increased risk of OA in other joints [2]. There is no cure for OA and the clinical and scientific focus has been on changing lifestyle factors that is associated with the development of OA and on limiting the development of OA in the adjacent joints.

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Since knee OA causes pain, reduced range of motion, and instability of the joint [3–6], patients alter their movement pattern to unload the knee [7–9]. Altering a movement pattern might increase the load on the hip and contralateral knee joint, and alter the pelvic movements [10]. Furthermore, a change in the proximal joints might affect the spine creating back pain for the patients [11]. Hence, it is important to further investigate movement alterations which might lead to overuse or overload of the other joints in patients with knee OA. Earlier studies of movement alterations have demonstrated that patients walk with reduced speed [7, 12], reduced knee flexion of the affected leg and trunk lean towards the more painful knee [8, 9]. Pelvic movement strategies during walking have only been sparsely investigated [9, 13], and we found no studies evaluating pelvic movement strategies for patients with medial compartment knee OA during more advanced tasks such as stair climbing and stepping onto a step. Patients with knee OA report problems with these activities [14], which could lead to compensatory strategies. Further investigation into differences in movements between patients and healthy controls during stair climbing and stepping could identify target areas for rehabilitation programs. Asay et al. [15] reported that during stair ascending, patients with more severe knee OA showed a greater forward trunk lean, which was suggested to be a compensatory strategy for weak knee extensor muscle strength. Particularly, lower limb muscle strength and muscle power, is a key finding in patients with knee OA [16–19]. A review of stair climbing performance for patients with knee OA found that greater quadriceps and hamstrings strength were related to greater stair climbing ability [20]. Moreover, it is well-known that muscle strength and functional performance are related in both elderly people and in patients with knee OA [21, 22]. For patients with a total knee replacement and for elderly people, leg extension power has an even closer relation to functional performance than leg strength [23, 24]. Hence, the purpose of the study was (1) to compare muscle power and pelvic range of motion between patients with knee OA and healthy controls and (2) to investigate crude and adjusted associations between muscle power and pelvic range of motion for patients with knee OA. We hypothesised that patients had leg extension power deficits, a larger pelvic range of motion in the sagittal and frontal plane during movements compared to controls, and that leg extension power of the affected leg would be inversely associated with a greater pelvic range of motion in the sagittal and frontal plane.

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Methods Design and material Preoperative data from an ongoing randomised clinical trial (RCT) (clinicaltrials.gov-ID: NCT01345825) was included in the present cross-sectional study. Patients with knee OA isolated in the medial compartment, scheduled for medial uni-compartmental knee arthroplasty (UKA) at Aarhus University Hospital, Denmark from February 2011 to June 2013 were included in the RCT. Patients were invited to participate if they were older than 18 years and living less than 40 km away from the hospital. Excluded were patients unable to comprehend the protocol instructions, patients with rheumatoid arthritis, neurological conditions that could affect functional performance, resting pain above 3 cm on a Visual Analogue Scale (VAS) [25] caused by other problems than the knee (e.g. hip or ankle pain) in the affected leg, and pain in the contralateral leg above 2 cm on a VAS. Healthy controls were included from September 2013 to February 2014 and were gender and age matched with the patients in a 1:2 ratio. The controls were recruited through the patients’ social network and through adverts in the municipality. Controls were considered ‘‘healthy’’ if they had no limitations in walking, no previous major surgery in their hips or knees (arthroscopy allowed), and no respiratory diseases that could affect functional performances. Patients and controls gave their written, informed consent prior to participation in accordance with the Declaration of Helsinki II. The Central Denmark Region Committee on Biomedical Research Ethics approved the study (M-20100185) and the Danish Data Protection Agency gave permission for the handling of personal data (2010-41-5089). Procedures Three testers were involved in the data collection of the patients and controls. All testers were trained according to a standardised test protocol before initiation of the study. Descriptive measures All patients and controls had their body mass measured and reported their height. Patients reported their resting pain and pain after activity on a 10 cm VAS-ruler [25]. Self-reported function and quality of life was recorded using the Knee injury and Osteoarthritis Outcome Score (KOOS) [26]. The KOOS consists of five subscales scored separately: pain, other symptoms, function in daily living, function in sport and recreation, and knee-related quality of

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life. The scores are transformed to a 0–100 ratio-scale, where 100 represents no knee-related problems. Missing data were handled as described in the KOOS Scoring Manual [27]. In patients with knee OA, test–retest reliability has been established in the range from ICC 0.60 to 0.97 [28]. In a comparative study of quality of life instruments, KOOS was evaluated to be one of the questionnaires that contained most items of importance to the patient [29]. Leg extension power The Nottingham Leg Extension Power-Rig (Nottingham University, Nottingham, United Kingdom) measured leg extension power in a single-leg simultaneous hip and knee extension separately for both legs. The subject applied maximal force, pushing a footplate which accelerated a flywheel from the starting position [30]. The subject had a knee flexion angle of 15° when the footplate was fully depressed. The subject was seated with arms crossed, slightly forward leaned, and instructed to extend the leg as quickly as possible with maximum effort. Standardised, verbal encouragement was provided during each trial. Three test-trials were performed before data collection began. The test was repeated with 30 s rest between trials until a plateau, defined as two successive measurements below the highest, was reached. A minimum of six trials (to minimize the learning effect), and a maximum of 10 trials (to minimize fatigue), were performed. The highest measurement in watt from a single attempt was normalized for body mass in kilograms and used as the data point. Test– retest reliability of measures from the Power-Rig is high in healthy people and in patients with end-stage knee OA, respectively [30, 31]. Movement analysis An inertia-based measurement unit (IMU) (Inertia-LinkÒ, MicroStrainÒ, Williston, United States of America) incorporates 3D gyroscopes, accelerometers, and magnetometer, which are reported to provide drift-free motion data. The IMU communicated with a PC using Bluetooth technology and calculates three degrees of freedom orientation data. The IMU was used for analyses of pelvic motion during walking, stair climbing and a block step test. The IMU was placed over the sacrum bone between the posterior superior iliac spines using double sided medical tape. Data was sampled at 100 Hz. The IMU measured trunk acceleration and angular pelvic motion in three dimensions [14], and via algorithms in MatLab 7.10.0Ò spatio-temporal estimates of pelvic range of motion could be derived [14, 32–34]. Range of motion was calculated as the mean difference between minimum and maximum angular pelvic motion.

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Trunk acceleration has been validated against force platforms and 3D motion capture where basic gait estimates showed an excellent agreement in elderly persons [35]. Furthermore, trunk and pelvic motion measured with IMU showed good agreement with 3D-motion capture for both young and elderly persons [34, 36]. Walking test Patients were instructed to walk 20 m between two marked lines in an undisturbed hallway with a concrete floor. Subjects were instructed to walk at their ‘‘usual, self-selected walking speed’’. A static starting procedure was applied, where the subjects started at the zero line and were asked to walk until the 20-m mark, pass it and stop [32]. The tester measured the distance from the 20-m mark to the front foot with a non-elastic tape measure. The test was performed twice separated by a break of at least 30 s. Blinded data analysis was performed using peak-detection algorithms that detected heel contacts and displayed anterior–posterior and vertical acceleration peaks—allowing the analyser to mark undetected peaks and delete incorrect peaks [37]. Derived estimates were: speed [meters/second (m/s)] and pelvic range of motion (pROM) in the sagittal and frontal planes [degrees (°)]. The average of gait estimates during two trials was used for further analysis. The estimate of walking speed derived has a high repeatability (ICC 0.90–0.99) and a good inter-observer reliability (ICC 0.77–0.92) in healthy people [32]. Stair climbing test A staircase (height: 16.5 cm, depth: 34 cm) was used to assess movement strategies during stair climbing. The use of handrails was not allowed. At self-selected speed, subjects ascended and descended five steps on a step-over-step manner twice. pROM in the sagittal and frontal planes during stair climbing was derived with an algorithm based on detection of start and completion of the test. The average estimate of pROM over two trials of five steps was used for further analysis. Block step test The block step test consisted of ascending and backward descending a 30 cm block step at self-selected speed. Three repetitions of stepping up and down with one leg were followed by three repetitions of stepping up and down with the other leg [14]. Subjects had to be able to complete at least three steps with each leg before the test was included for further analysis. pROM in the sagittal and frontal planes was derived with an algorithm based on detection of

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initiation and completion of each step and average estimates of three steps were derived. Sample size Sample size was calculated based on preoperative leg extension power measures derived from Barker et al. [19]. With a 2:1 ratio, 5 % level of significance and statistical power of 80 %, the groups were estimated to consist of: n = 57 (patients) and n = 29 (controls) [38]. Sample size was calculated a priori and inclusion of controls stopped when the target number was reached. Statistical methods Data was tested for normality by inspection of Q–Q plots and histograms. Differences between patients and controls were evaluated by linear multiple regression modelling if the assumptions for the model were met [39], adjusted for age, gender and body mass [30, 40]. A secondary model was made to test differences in pelvic motion during walking when adjusted for walking speed [34, 41]. Associations between leg extension power and pROM were investigated by linear multiple regression modelling. One model (crude) was made with leg extension power and pROM in patients, and then age, gender and body mass were added in a second model (adjusted). The significance level was set to 0.05 and all statistical analyses were made in Stata 12.1 (StataCorp, College Station, TX) software package.

Results Out of 189 patients eligible for surgery, 64 declined to participate, while 68 were excluded leaving 57 patients for inclusion. In total, 38 healthy persons volunteered to participate, of whom, four persons did not match any patient and five persons met the exclusion criteria, leaving 29 controls for inclusion (Fig. 1). All patients completed the test in the Power-Rig. One patient did not complete the KOOS pain subscale and two patients did not complete the KOOS sports and recreation subscale. Two patients (4 %) were unable to ascend stairs, six patients were unable to descend stairs (11 %), and nine patients (16 %) were unable to complete the block step test. For three patients, the walking test could not be analysed due to measurement errors, which was also the case for one stair ascending test, one stair descending test, and two block step tests. All controls completed all tests and it was possible to analyse all their data.

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Patients and controls did not differ significantly in age and gender (P = 0.83), but were significantly different in body mass and body mass index (P \ 0.01) (Table 1). Patients had a lower score (P \ 0.01) in all KOOS subscales, with the lowest median score in the sports and recreation subscale (Fig. 2). Leg extension power and self-selected walking speed There was no difference in leg extension power between the two legs of the controls (P = 0.91), whereas the patients’ affected leg was significantly weaker than the contralateral leg (20 % weaker) (P \ 0.01). Both the affected (39 % weaker) and the contralateral (20 % weaker) legs of the patients were significantly weaker than the controls (P \ 0.01) (Table 1). Patients had a significantly slower self-selected walking speed than controls (P \ 0.01). Pelvic range of motion Sagittal plane Patients and controls showed no difference in the sagittal plane pROM during level ground walking (P = 0.89). During stair descending and block step ascending and descending, patients had significantly larger pROM compared with controls (P B 0.03) (Fig. 3). Frontal plane During walking, controls had a significantly larger pROM than patients, which remained significant after adjusting for walking speed. Increasing walking speed was associated with increasing pROM (P = 0.01). Patients had a significantly larger pROM when descending stairs and descending the block step (Fig. 4) (P \ 0.01), but did not differ during ascending (P [ 0.06). Associations between leg extension power and pelvic range of motion for the patients No associations were seen between leg extension power and pROM during level ground walking in neither the sagittal nor the frontal plane (Table 2). In the sagittal plane, leg extension power was inversely associated with pROM during stair and block step ascending and descending (P B 0.02), but when including age, gender and body mass in the model, power was only associated with sagittal pROM during stair descending and step descending (P B 0.01) (Table 2).

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Fig. 1 Flowchart.  Declined: 35 because of transportation problems, 17 unknown reason, 9 because they were too busy for the intervention and three because they did not want the intervention. àReasons for exclusion: 22 had contralateral pain, 13 were not possible to get in contact with before surgery, 10 had surgery earlier than planned, six for unknown reasons, five cancelled surgery, four had a neurological disease, two were converted to total knee replacement, two had a

lateral knee replacement, two had severe contralateral osteoarthritis, one was recommended not to participate by general practitioner and one had allergy towards pain medication. §Reasons for exclusion: two had planned knee surgery, one had planned hip replacement surgery, one had a toe fracture and one had chronic obstructive lung disease. KOOS Knee injury and Osteoarthritis Outcome Score

Table 1 Demographics, pain scores, leg extension power and walking speed Patients

Controls

P value

n

Mean (SD)

n

Mean (SD)

Age (years)

57

65.6 (7.6)

29

66.0 (7.9)

Gender (number of males, %)

57

Body weight (kg)

57

Demographics and pain scores 28 (47 %) 86.0 (15.2)

0.83

29

14 (48 %)

0.94

29

74.8 (13.5)

\0.01

Height (m)

57

1.72 (0.09)

29

1.73 (0.10)

0.19

Body mass index (kg/m2)

57

29.1 (4.1)

29

24.8 (3.3)

\0.01

Pain in affected knee at rest (VAS score, cm)

57

–

–

–

–

Pain in affected knee after test (VAS score, cm)

56

1.2 (0, 3.2)  4.5 (1.7, 6.1)

 

Leg extension power and walking speed 57

1.18 (0.81, 1.66) 

29

1.93 (1.51, 2.43) 

\0.01

Max power/body weight: contralateral leg/left (W/kg)

57

 

1.48 (0.99, 2.09)

29

1.85 (1.67, 2.34) 

\0.01

Max power: affected leg/right (W)

57

104 (70, 146) 

29

129 (105, 217) 

\0.01à

Max power: contralateral leg/left (W)

57

122 (81, 197) 

29

141 (107, 183) 

Max power/body weight: affected leg/right (W/kg)

Self-selected walking speed (m/s)

54

 

Data was skewed and is presented with median, 25th and 75th quartile

à

Significant coefficient for body mass

 

1.18 (1.01, 1.26)

29

0.02à  

1.40 (1.32, 1.50)

\0.01

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15

20

10

40

60

Degrees (°)

80

20

100

1222

0

Controls

Walking

Pain

Symptoms

ADL

Sport/rec

Controls

Stair ascending Stair descending Step ascending Step descending

QoL

30

Fig. 2 Knee injury and Osteoarthritis Outcome Score. Median values and interquartile ranges. *Significant difference between patients and controls (P \ 0.05). ADL activities of daily living, Sport/rec sports and recreation, QoL knee-related quality of life

Fig. 4 Pelvic range of motion in the frontal plane. Median values and interquartile ranges. *Significant differences between patients and controls (P\ 0.05). Patients used significantly greater pelvic range of motion during stair and step descending while it is the opposite case during walking

15 10

20

25

than controls and generally used a greater pROM during more advanced tasks particularly when these involved descending. Furthermore, an inverse association between leg extension power and pROM during stair and block step descending was found. Leg extension power The findings of lower leg extension power in the group of patients with end-stage medial compartment OA correspond to the findings of Barker et al. [19], who detected leg extension power values of 0.83 W/kg in the affected leg and 1.22 W/kg in the contralateral leg, while we found median values of 1.18 W/kg for the affected leg and 1.48 W/kg for the contralateral leg. The slightly greater values in the present study may be explained by differences in patient selection, since Barker et al. [19] included a cohort sample, while our study included patients who were scheduled for surgery and already enrolled in a RCT. In contrast, the values of our control group (1.85–1.93 W/kg) were lower than reference values published by Skelton et al. [42], where the mean value of men and women aged 65–79 years was 2.12 W/kg. However, our control group showed greater KOOS scores compared to populationbased reference data from more than 500 Swedish persons [43], and consequently, it is not suspected that knee problems could explain the lower leg extension power values in the control group. The differences could be caused by different study protocols in terms of different start angles in the Power-Rig, which has been shown to affect the outcome [44]. Despite the slight discrepancy towards published norm data, significant differences between patients and controls were still evident for both

5

Degrees (°)

Patients

5

Patients

Walking

Patients

Controls

Stair ascending Stair descending Step ascending Step descending

Fig. 3 Pelvic range of motion in the sagittal plane. Median values and interquartile ranges. *Significant differences between patients and controls (P \ 0.05)

In the frontal plane, leg extension power was only associated with pROM during stair descending (P B 0.02), which remained significant after adjusting for age, gender and body mass (P B 0.04). In the adjusted analyses, age was found to have a significant association with pROM in the sagittal plane during stair ascending and with pROM in the frontal plane during stair and step ascending, while no associations for body mass were significant (Table 2).

Discussion The aim of the study was to investigate leg extension power and pROM in patients with medial knee OA compared with controls. Patients had lower leg extension power

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Table 2 Associations between leg extension power and pelvic range of motion Associations

n

Affected leg

Contralateral leg

Coefficient

Confidence interval (95 %)

P value

Adjusted R2

Coefficient

Confidence interval (95 %)

P value

Adjusted R2

Crude Sagittal plane Walking Stair ascending

54 54

-0.004 -0.03

(-0.01, 0.004) (-0.05, -0.004)

0.28 0.02*

0 0.1

-0.01 -0.03

(-0.01, 0.001) (-0.05, -0.01)

0.07 \0.01*

0.04 0.14

Stair descending

50

-0.04

(-0.06, -0.02)

0.01*

0.19

-0.03

(-0.05, -0.01)

\0.01*

0.17

Step ascending

46

-0.05

(-0.08, -0.02)

\0.01*

0.2

-0.05

(-0.08, -0.03)

\0.01*

0.25

Step descending

46

-0.03

(-0.06, -0.01)

\0.01*

0.18

-0.03

(-0.05, -0.01)

0.01*

0.13

Walking

54

0

(-0.01, 0.01)

0.35

0

0

(-0.01, 0.01)

0.88

-0.02

Stair ascending

54

-0.01

(-0.03, 0.01)

0.17

0.02

-0.01

(-0.03, 0.01)

0.39

0

Stair descending

50

-0.03

(-0.05, -0.02)

\0.01*

0.22

-0.03

(-0.05, -0.01)

0.01*

0.12

Step ascending

46

0

(-0.02, 0.01)

0.7

-0.02

-0.002

(-0.02, 0.01)

0.78

-0.02

Step descending

46

-0.01

(-0.02, 0.01)

0.25

0.01

-0.01

(-0.02, 0.01)

0.23

0.01

54

0

(-0.01, 0.01)

0.91

0.43

Frontal plane

Adjusted Sagittal plane Walking

0

(-0.02, 0.01)

 

Stair ascending

54

-0.01

(-0.04, 0.01)

0.32

-0.02

(-0.05, 0.01)

0.18

Stair descending Step ascending

50 46

-0.03 -0.03

(-0.06, -0.01) (-0.07, 0.01)

0.01* 0.12

-0.03 -0.04

(-0.06, 0) (-0.08, 0.003)

0.05 0.07

Step descending

46

-0.04

(-0.07, -0.01)

0.01*

-0.04

(-0.07, -0.01)

0.02*

Walking

54

0.01

(-0.002, 0.02)

0.10à

0

(-0.01, 0.01)

0.82

Stair ascending

54

-0.01

(-0.04, 0.01)

0.13 

-0.01

(-0.04, 0.01)

0.25 

Stair descending

50

-0.03

(-0.05, -0.005)

0.02*

-0.03

(-0.05, -0.002)

0.04*

Step ascending

46

-0.01

(-0.03, 0.02)

0.59 

-0.01

(-0.03, 0.01)

0.36 

-0.02

(-0.04, 0.003)

0.09 

Frontal plane

Step descending

46

-0.01

(-0.03, 0.01)

0.30

 ,à

No coefficient for body weight was significant in any analyses * A significant association between leg extension power and pelvic range of motion (P \ 0.05)  

Significant association (P \ 0.05) between age and pelvic range of motion

à

Significant difference (P \ 0.05) between the genders was found

legs, clearly supporting the existing knowledge of general impairments of muscle function in the patient group. Pelvic range of motion during walking The pROM in the frontal plane was significantly increased with faster walking speed. This is in accordance with the results reported in a study of healthy, young subjects [41]. Also in line with the present findings, Bolink et al. [14] reported significantly greater pROM for controls than for patients. Of note, however, their patients walked significantly slower than the controls, which may have affected the pROM since no adjustment was made. In earlier studies, contralateral pelvic drop during walking has been discussed [9, 13]. Our patients did not exhibit an increased contralateral pelvic drop during

walking. There are several possible explanations for this. First, walking speed clearly affected the movements, why elimination of this factor seems necessary before clear conclusions about the pROM during walking for patients with medial knee OA can be made. Second, the IMU can only measure the pROM and not the drop alone, which differs from 3D-motion capture systems. However, applying 3D-motion capture, Hunt et al. [9] similarly found a tendency of smaller pelvic movement in the frontal plane during walking for patients with medial knee OA compared to controls. Further, Hunt et al. [9] reported an increased lateral trunk lean towards the affected leg, and analysis into the pelvic movements indicated that this may have affected the contralateral iliac spine to be lifted up, hereby minimising the movements of the pelvis. It is therefore necessary to investigate pelvic drop during standardised

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walking speeds and simultaneously record lateral trunk lean before conclusions about pelvic movements during walking can be made. Pelvic movement strategies during ascending During stair and block step ascending, patients used significantly greater pROM in the sagittal plane, but not in the frontal plane. Similar results have been found in patients listed for total knee replacement [14]. In our study, we found an inverse association between the sagittal plane pROM and leg extension power in the crude model for the affected leg. This supports the suggestion of Asay et al. [15], where it was stated that compensatory movements could be associated with reduced knee extensor muscle strength. However, when adding age, gender and body mass in the adjusted model, only age was associated with pROM. Furthermore, in the adjusted analyses, age was significantly associated with pROM in the frontal plane during both stair and step ascending, which was not the case for the other factors in the model. The present study indicates that a change in pelvic movements during ascending occurs with age rather than with decreasing leg extension power. Similar results were found by Skelton et al. [42], where age explained more of the variance in the ability to step up than leg extension power for elderly persons. Still patients used greater pROM than controls in the sagittal plane, even when adjusted for age. This indicates that other limitations for the patients than lower leg extension power affects the movement strategies. Pelvic movement strategies during descending To our knowledge, this is the first study to investigate pelvic movements during descending in patients with medial knee OA. During both forward and backward descending, patients used a larger pROM in both planes. Interestingly, the adjusted regression analyses showed associations between leg extension power and pROM during stair descending, while no clear association with pROM was found during ascending. Since there is a greater force output while descending [45], this might explain why power is closely associated with pelvic movements during descending. The patients might have enough power to perform an ascending task at self-selected speed, but when they have to descend, compensatory strategies are needed. In a study, concentric and eccentric maximal muscle strength was investigated in patients with knee OA and it was found that especially eccentric maximal force was decreased in the patient group [46]. In line with our findings, this indicates that a greater focus on descending tasks (or on eccentric muscle contractions) should be emphasised in rehabilitation programs for this patient group. The

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associations in our study were significant; however, the coefficients of determination were low, and hence future studies could investigate if a stronger association exists between eccentric muscle strength and movement strategies during descending. Clinical implications Often human movement is characterised by being the most energy efficient movement strategy for the given daily activity. When movement strategies change, it is often an indication of pain or reduced ability to stabilise a skeletal segment. Altered movement strategies might overload or overuse other joints [10, 11]. An altered movement pattern has earlier been linked to fatigue for patients with knee OA since the altered movements demand an inefficient energy use [47]. Hence, there should be a focus at normalising the movement pattern for the patients [47]. In the present study, it was found that leg extension power was associated with increased pelvic movements during descending. Hence, gaining more strength might serve to normalise the movement pattern. Ongoing studies (clinical trials identifier: NCT01647243, NCT01345825) have been designed to test if an intervention aimed at increasing muscle strength before or after knee surgery will improve patients’ functional outcomes, and these results might highlight a possible improvement for the patients in the future. Furthermore, it is at best uncertain whether the knee surgery alone will result in a normalisation of the movement pattern. However, we know that patients report problems with stair climbing and physical performance after knee surgery [20], which underlines that the surgical procedure is not enough to enable participation in daily activities for the patients. Consequently, the findings of the present study could be used to benefit the patients in a way that the identified relationship between pelvic ROM and leg muscle strength may serve as a potential target for an intervention (e.g. resistance training) which may improve the mobility of the patients and thereby benefit them pre- or postoperatively. Study limitations There are a number of limitations that influence the interpretation and conclusion of the present study. First, we used a slightly different measurement of pelvic movement than those used in earlier studies. The IMU only measures pROM and not pelvic drop and tilt as measured with 3D-motion capture. Hence, we do not know if the movement performed in the sagittal plane is a forward or backward tilt of the pelvis. Second, there was a significant difference in body mass between patients and controls. However, the effect of body

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mass was not significant in any of the performed analyses involving pROM. Moreover, only leg extension power was significantly affected by body mass, which is an expected finding. We therefore consider our results of differences in pROM between patients and controls to be valid despite the difference in body mass between the groups. Third, no control of movement speed was performed during stair climbing and stepping. During faster walking speed, an increase in pelvic movements was observed. It was not possible to quantitatively measure speed of stair climbing and stepping, though qualitatively, it was observed that patients moved slower during these movements than the control group. However, this means that if the patients had climbed and stepped with the same speed as the controls, and if the identical relationship (pelvic movements increase with speed) exists during these movements, then, the difference in pelvic movement would have been even larger than reported in this study. However, we do not know if such a relationship exists during more advanced tasks. Fourth, 16 % of the patients could not complete the block step test and hence the results of the block step test limit the generalizability of the results. This also suggests that special attention to stepping ought to be provided in rehabilitation programs. Finally, the cross-sectional design does not allow conclusions on causal relationships between movement strategies and disease-specific progression, suggesting future longitudinal studies.

Conclusion In conclusion, patients with end-stage medial knee OA (1) had decreased leg extension power and increased pROM during more advanced tasks when compared to controls, and (2) showed associations between leg extension power and pROM during most descending movements. Acknowledgments Supported by the Bevica Foundation, provided inertia measurement unit for measurement of pelvic motion. Conflict of interest

None.

References 1. Wengler A, Nimptsch U, Mansky T (2014) Hip and knee replacement in Germany and the USA: analysis of individual inpatient data from German and US hospitals for the years 2005–2011. Deutsches Arzteblatt Int 111(23–24):407–416. doi:10.3238/arztebl.2014.0407 2. Prieto-Alhambra D, Judge A, Javaid MK, Cooper C, Diez-Perez A, Arden NK (2014) Incidence and risk factors for clinically diagnosed knee, hip and hand osteoarthritis: influences of age, gender and osteoarthritis affecting other joints. Ann Rheum Dis 73(9):1659–1664. doi:10.1136/annrheumdis-2013-203355

1225 3. Felson DT (2009) Developments in the clinical understanding of osteoarthritis. Arthritis Res Ther 11(1):203. doi:10.1186/ar2531 4. Astephen JL, Deluzio KJ, Caldwell GE, Dunbar MJ, HubleyKozey CL (2008) Gait and neuromuscular pattern changes are associated with differences in knee osteoarthritis severity levels. J Biomech 41(4):868–876. doi:10.1016/j.jbiomech.2007.10.016 5. Kumar D, Swanik CB, Reisman DS, Rudolph KS (2014) Individuals with medial knee osteoarthritis show neuromuscular adaptation when perturbed during walking despite functional and structural impairments. J Appl Physiol (Bethesda, Md : 1985) 116(1):13–23. doi:10.1152/japplphysiol.00244.2013 6. van der Esch M, Knoop J, van der Leeden M, Voorneman R, Gerritsen M, Reiding D, Romviel S, Knol DL, Lems WF, Dekker J, Roorda LD (2012) Self-reported knee instability and activity limitations in patients with knee osteoarthritis: results of the Amsterdam osteoarthritis cohort. Clin Rheumatol 31(10):1505–1510. doi:10.1007/s10067-012-2025-1 7. da Silva HG, Cliquet Junior A, Zorzi AR, Batista de Miranda J (2012) Biomechanical changes in gait of subjects with medial knee osteoarthritis. Acta Ortop Bras 20(3):150–156. doi:10.1590/ s1413-78522012000300004 8. Creaby MW, Bennell KL, Hunt MA (2012) Gait differs between unilateral and bilateral knee osteoarthritis. Arch Phys Med Rehabil 93(5):822–827. doi:10.1016/j.apmr.2011.11.029 9. Hunt MA, Wrigley TV, Hinman RS, Bennell KL (2010) Individuals with severe knee osteoarthritis (OA) exhibit altered proximal walking mechanics compared with individuals with less severe OA and those without knee pain. Arthritis Care Res 62(10):1426–1432. doi:10.1002/acr.20248 10. Mundermann A, Dyrby CO, Andriacchi TP (2005) Secondary gait changes in patients with medial compartment knee osteoarthritis: increased load at the ankle, knee, and hip during walking. Arthritis Rheum 52(9):2835–2844. doi:10.1002/art. 21262 11. Bejek Z, Paroczai R, Illyes A, Kiss RM (2006) The influence of walking speed on gait parameters in healthy people and in patients with osteoarthritis. Knee Surg Sports Traumatol Arthrosc 14(7):612–622. doi:10.1007/s00167-005-0005-6 12. Chen CP, Chen MJ, Pei YC, Lew HL, Wong PY, Tang SF (2003) Sagittal plane loading response during gait in different age groups and in people with knee osteoarthritis. Am J Phys Med Rehabil Assoc Acad Physiatr 82(4):307–312. doi:10.1097/01.phm. 0000056987.33630.56 13. Bennell KL, Hunt MA, Wrigley TV, Hunter DJ, McManus FJ, Hodges PW, Li L, Hinman RS (2010) Hip strengthening reduces symptoms but not knee load in people with medial knee osteoarthritis and varus malalignment: a randomised controlled trial. Osteoarthr Cartil OARS Osteoarthr Res Soc 18(5):621–628 14. Bolink SA, van Laarhoven SN, Lipperts M, Heyligers IC, Grimm B (2012) Inertial sensor motion analysis of gait, sit-stand transfers and step-up transfers: differentiating knee patients from healthy controls. Physiol Meas 33(11):1947–1958. doi:10.1088/ 0967-3334/33/11/1947 15. Asay JL, Mundermann A, Andriacchi TP (2009) Adaptive patterns of movement during stair climbing in patients with knee osteoarthritis. J Orthop Res 27(3):325–329. doi:10.1002/jor. 20751 16. Liikavainio T, Lyytinen T, Tyrvainen E, Sipila S, Arokoski JP (2008) Physical function and properties of quadriceps femoris muscle in men with knee osteoarthritis. Arch Phys Med Rehabil 89(11):2185–2194. doi:10.1016/j.apmr.2008.04.012 17. Palmieri-Smith RM, Thomas AC, Karvonen-Gutierrez C, Sowers MF (2010) Isometric quadriceps strength in women with mild, moderate, and severe knee osteoarthritis. Am J Phys Med Rehabil Assoc Acad Physiatr 89(7):541–548. doi:10.1097/PHM. 0b013e3181ddd5c3

123

1226 18. Ruhdorfer A, Dannhauer T, Wirth W, Hitzl W, Kwoh CK, Guermazi A, Hunter DJ, Benichou O, Eckstein F (2013) Thigh muscle cross-sectional areas and strength in advanced versus early painful osteoarthritis: an exploratory between-knee, withinperson comparison in osteoarthritis initiative participants. Arthritis Care Res 65(7):1034–1042. doi:10.1002/acr.21965 19. Barker KL, Jenkins C, Pandit H, Murray D (2012) Muscle power and function 2 years after unicompartmental knee replacement. Knee 19(4):360–364. doi:10.1016/j.knee.2011.05.006 20. Whitchelo T, McClelland JA, Webster KE (2013) Factors associated with stair climbing ability in patients with knee osteoarthritis and knee arthroplasty: a systematic review. Disabil Rehabil. doi:10.3109/09638288.2013.829526 21. O’Reilly SC, Jones A, Muir KR, Doherty M (1998) Quadriceps weakness in knee osteoarthritis: the effect on pain and disability. Ann Rheum Dis 57(10):588–594 22. Chun SW, Kim KE, Jang SN, Kim KI, Paik NJ, Kim KW, Jang HC, Lim JY (2013) Muscle strength is the main associated factor of physical performance in older adults with knee osteoarthritis regardless of radiographic severity. Arch Gerontol Geriatr 56(2):377–382. doi:10.1016/j.archger.2012.10.013 23. Puthoff ML, Nielsen DH (2007) Relationships among impairments in lower-extremity strength and power, functional limitations, and disability in older adults. Phys Ther 87(10):1334–1347. doi:10.2522/ptj.20060176 24. Aalund PK, Larsen K, Hansen TB, Bandholm T (2013) Normalized knee-extension strength or leg-press power after fasttrack total knee arthroplasty: which measure is most closely associated with performance-based and self-reported function? Arch Phys Med Rehabil 94(2):384–390 25. Hawker GA, Mian S, Kendzerska T, French M (2011) Measures of adult pain: visual Analog Scale for Pain (VAS Pain), Numeric Rating Scale for Pain (NRS Pain), McGill Pain Questionnaire (MPQ), Short-Form McGill Pain Questionnaire (SF-MPQ), Chronic Pain Grade Scale (CPGS), Short Form-36 Bodily Pain Scale (SF-36 BPS), and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP). Arthritis Care Res 63(Suppl 11):S240–S252. doi:10.1002/acr.20543 26. Roos EM, Roos HP, Ekdahl C, Lohmander LS (1998) Knee injury and Osteoarthritis Outcome Score (KOOS)––validation of a Swedish version. Scand J Med Sci Sports 8(6):439–448 27. Roos E (2012) KOOS scoring manual 2012. Ewa Roos. koos. nu. Accessed 04/23 2014 28. Collins NJ, Roos EM (2012) Patient-reported outcomes for total hip and knee arthroplasty: commonly used instruments and attributes of a ‘‘good’’ measure. Clin Geriatr Med 28(3):367–394. doi:10.1016/j.cger.2012.05.007 29. Tanner SM, Dainty KN, Marx RG, Kirkley A (2007) Kneespecific quality-of-life instruments: which ones measure symptoms and disabilities most important to patients? Am J Sports Med 35(9):1450–1458. doi:10.1177/0363546507301883 30. Bassey EJ, Short AH (1990) A new method for measuring power output in a single leg extension: feasibility, reliability and validity. Eur J Appl Physiol 60(5):385–390 31. Villadsen A, Roos EM, Overgaard S, Holsgaard-Larsen A (2012) Agreement and reliability of functional performance and muscle power in patients with advanced osteoarthritis of the hip or knee. Am J Phys Med Rehabil Assoc Acad Physiatr 91(5):401–410. doi:10.1097/PHM.0b013e3182465ed0 32. Senden R, Grimm B, Heyligers IC, Savelberg HH, Meijer K (2009) Acceleration-based gait test for healthy subjects:

123

Arch Orthop Trauma Surg (2015) 135:1217–1226

33.

34.

35.

36.

37.

38.

39. 40.

41.

42.

43.

44.

45.

46.

47.

reliability and reference data. Gait Posture 30(2):192–196. doi:10.1016/j.gaitpost.2009.04.008 Zijlstra W, Hof AL (2003) Assessment of spatio-temporal gait parameters from trunk accelerations during human walking. Gait Posture 18(2):1–10 Zijlstra A, Goosen JH, Verheyen CC, Zijlstra W (2008) A bodyfixed-sensor based analysis of compensatory trunk movements during unconstrained walking. Gait Posture 27(1):164–167. doi:10.1016/j.gaitpost.2007.02.010 Hartmann A, Luzi S, Murer K, de Bie RA, de Bruin ED (2009) Concurrent validity of a trunk tri-axial accelerometer system for gait analysis in older adults. Gait Posture 29(3):444–448. doi:10. 1016/j.gaitpost.2008.11.003 Wong WY, Wong MS (2008) Trunk posture monitoring with inertial sensors. Eur Spine J 17(5):743–753. doi:10.1007/s00586008-0586-0 Gonzalez RC, Lopez AM, Rodriguez-Uria J, Alvarez D, Alvarez JC (2010) Real-time gait event detection for normal subjects from lower trunk accelerations. Gait Posture 31(3):322–325. doi:10. 1016/j.gaitpost.2009.11.014 Suresh K, Chandrashekara S (2012) Sample size estimation and power analysis for clinical research studies. J Hum Reprod Sci 5(1):7–13. doi:10.4103/0974-1208.97779 Altman DG (1991) Practical statistics for medical research. Chapman & Hall, London Taylor N, Evans O, Goldie P (2001) Reliability of measurement of angular movements of the pelvis and lumbar spine during treadmill walking. Physiother Res Int 6(4):205–223 Taylor NF, Goldie PA, Evans OM (1999) Angular movements of the pelvis and lumbar spine during self-selected and slow walking speeds. Gait Posture 9(2):88–94 Skelton DA, Greig CA, Davies JM, Young A (1994) Strength, power and related functional ability of healthy people aged 65–89 years. Age Ageing 23(5):371–377 Paradowski PT, Bergman S, Sunden-Lundius A, Lohmander LS, Roos EM (2006) Knee complaints vary with age and gender in the adult population. Population-based reference data for the Knee injury and Osteoarthritis Outcome Score (KOOS). BMC Musculoskelet Disord 7:38. doi:10.1186/1471-2474-7-38 Barker KL, Crystal C, Newman M (2012) Effect of different angles of knee flexion on leg extensor power in healthy individuals. Physiotherapy 98(4):357–360. doi:10.1016/j.physio. 2012.03.001 Hasegawa M, Chin T, Oki S, Kanai S, Shimatani K, Shimada T (2010) Effects of methods of descending stairs forwards versus backwards on knee joint force in patients with osteoarthritis of the knee: a clinical controlled study. Sports Med Arthrosc Rehabil Ther Technol SMARTT 2:14. doi:10.1186/1758-2555-214 Hortobagyi T, Garry J, Holbert D, Devita P (2004) Aberrations in the control of quadriceps muscle force in patients with knee osteoarthritis. Arthritis Rheum 51(4):562–569. doi:10.1002/art. 20545 Sparling TL, Schmitt D, Miller CE, Guilak F, Somers TJ, Keefe FJ, Queen RM (2014) Energy recovery in individuals with knee osteoarthritis. Osteoarthr Cartil OARS Osteoarthr Res Soci. doi:10.1016/j.joca.2014.04.004