Elsevier

Gait & Posture

Volume 37, Issue 3, March 2013, Pages 440-444
Gait & Posture

Gait biomechanics and hip muscular strength in patients with patellofemoral osteoarthritis

https://doi.org/10.1016/j.gaitpost.2012.08.017Get rights and content

Abstract

A significant number of patients with patellofemoral osteoarthritis (PFOA) have described a history of patellofemoral pain syndrome (PFPS). This leads to speculation that the underpinning mechanical causes of PFPS and PFOA may be similar. Although alterations in gait biomechanics and hip strength have been reported in PFPS, this relationship has not yet been explored in PFOA. Therefore the purpose of this study was compare gait biomechanics and hip muscular strength between PFOA patients and a healthy control group. Fifteen patients with symptomatic, radiographic PFOA and 15 controls participated. All patients underwent a walking gait analysis and maximal hip strength testing. Biomechanical variables of interest included the peak angular values of contra-lateral pelvic drop, hip adduction and hip internal rotation during the stance phase. Hip abduction and external rotation strength were assessed using maximal voluntary isometric contractions. The PFOA group demonstrated significantly lower hip abduction strength compared to controls but no difference in hip external rotation strength. There were no statistical differences between the PFOA and control groups for contra-lateral pelvic drop, hip adduction and hip internal rotation angles during walking. Despite patients with PFOA exhibiting weaker hip abductor muscle strength compared to their healthy counterparts they did not demonstrate alterations in pelvis or hip biomechanics during gait. These preliminary data suggests that weaker hip abductor strength does not result in biomechanical alterations during gait in this population.

Highlights

► Patients with patellofemoral osteoarthritis (PFOA) demonstrated weaker hip abduction strength compared to healthy controls. ► PFOA patients demonstrated no difference in hip external rotation strength compared to controls. ► PFOA patients showed no differences in hip adduction/internal rotation or pelvic drop during gait compared to controls. ► Decrements in hip abduction strength are not necessarily accompanied by changes in gait in a PFOA population.

Introduction

Osteoarthritis (OA) is the most common joint disease in the world [1]. However, the aetiology of this disease remains unclear and there are currently no known treatments that have been proven to slow its progression. The knee is one of the most commonly affected joints and represents a major cause of pain and disability [2]. Traditionally, knee OA has been viewed as a disorder of the tibiofemoral joint, particularly of the medial compartment. However, studies have shown that 22–33% of knee OA patients exhibit osteoarthritic changes in the patellofemoral joint [3], [4], [5]. Additionally, compared with medial compartment OA, PFOA patients are more likely to report disability [4], [5] and suffer an earlier onset of chronic symptoms [4], [6].

Due to a current lack of literature investigating the biomechanical gait patterns associated with PFOA, it is pertinent to examine other patellofemoral disorders to help elucidate potential mechanisms. A study of PFOA patients waiting to undergo an arthroplasty showed that 22% of them described preceding patellofemoral pain syndrome (PFPS) in their adolescence and early adult years [6]. This finding is perhaps not surprising since up to 78% of PFPS patients still report chronic pain 5–20 years after rehabilitation [7], [8], [9]. The longevity of PFPS along with the low success rate following rehabilitation, leads to the hypothesis that the underpinning mechanical causes of PFPS and PFOA may be similar. This hypothesis is based on the premise that abnormal biomechanical patterns associated with the aetiology of PFPS may also contribute to degenerative changes at the patellofemoral joint over time.

Although the exact aetiology of PFPS remains unknown, some studies have shown excessive hip adduction and internal rotation during gait to be present in PFPS patients [10], [11], [12]. It is possible that abnormal hip mechanics are responsible for symptoms since several cadaveric studies have provided evidence for a link between abnormal lower extremity alignment and altered loading at the patellofemoral joint [13], [14]. Excessive hip adduction may result in a medial collapse of the supporting limb and a theoretical increase in the quadriceps angle during stance (knee abduction). In turn, an increased quadriceps angle has been shown to result in elevated patellofemoral contact pressure [14]. Similarly, greater internal rotation of the femur was reported to also lead to increased patellofemoral contact pressure [13]. Therefore, alterations in gait kinematics could theoretically alter the contact pressure experienced in the patellofemoral joint, thus placing the underlying cartilage at risk for subsequent damage and degeneration.

Hip muscular strength has also received attention in the literature with respect to its association with PFPS. In particular, PFPS patients demonstrated decrements of 15–21% and 15–36% in hip abductor and hip external rotator strength respectively when compared to a healthy control group [15], [16], [17]. Moreover, reduced hip abductor and external rotator muscle strength has been associated with excessive hip abduction [16] and internal rotation [12] during gait respectively, suggesting that reduced hip muscle force output may be partly responsible for the atypical hip biomechanics.

Considering the epidemiological link between PFPS and PFOA, it is possible that the abnormal hip biomechanics and weakness of the hip musculature found in PFPS patients may also be contributing factors to PFOA. However, there is a dearth of literature examining muscular strength and gait biomechanics in patients with knee osteoarthritis whose symptoms originate primarily in the patellofemoral joint. Therefore, the purpose of this study was to investigate differences in hip strength and gait biomechanics between patients with mild to moderate PFOA and asymptomatic controls. It was hypothesised that compared to controls, PFOA patients would demonstrate greater hip adduction, hip internal rotation and contralateral pelvic drop during walking together with reduced hip abduction and external rotation muscular strength.

Section snippets

Subjects

Fifteen male and female subjects diagnosed with PFOA were recruited for the study. Fifteen gender matched asymptomatic subjects served as a control group (CON). Demographic data for all subjects can be found in Table 1. There were no significant differences between the PFOA and CON group in terms of age, mass or BMI. The sample size was selected following an a priori power analysis on the variable with the largest standard deviation (SD) noted in previous literature, peak hip internal rotation

Results

The PFOA and CON groups were well matched in terms of mass and BMI (Table 1). There were no significant between-group differences in either peak angle or angular excursion variables for pelvic drop, hip adduction, hip internal rotation and knee abduction (Table 2). Effect sizes for all kinematic variables were also generally low. A post hoc analysis was conducted comparing the biomechanical variables of interest between the two groups when only the female subjects were included (N = 12). There

Discussion

The goal of this study was to investigate differences in hip strength and gait biomechanics between patients with mild to moderate patellofemoral osteoarthritis and asymptomatic controls. Contrary to the hypothesis, no differences in hip biomechanics during walking were found between the two groups. However, evidence for a hip muscle strength discrepancy was partially supported with the PFOA group demonstrating significantly decreased hip abduction strength.

The lack of pelvis and hip kinematic

Conflict of interest

There are no conflicts of interest for any of the authors.

Acknowledgements

This study was funded by Alberta Innovates: Health Solutions and Alberta Innovates: Technology Futures. The authors gratefully acknowledge the assistance of Kimber Thornton, Jill Baxter, Chandra Lloyd, Sang-Kyoon Park and Lindsay Farr.

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