Do subjects with Patellofemoral Pain Syndrome have abnormal segmental rotation of the hip (2006)

Introduction: Patellofemoral Pain Syndrome (PFPS) is one of the most prevalent knee disorders1. Although the aetiology is unknown it is commonly believed that abnormal patella tracking and altered lower limb kinematics are involved. A common clinical hypothesis is that patients with PFPS demonstrate excessive hip internal rotation during activities which involve hip and knee flexion, leading to an increased lateral vector force at the patella. The aim of this study was to perform a kinematic comparison of hip segmental rotation in healthy and PFPS subjects. Methodology: Fourteen healthy volunteers (7 males and 7 females, mean age (±SD) 30.5 ± 6.49) with no history of knee pathology and 9 patients with PFPS (2 males and 7 females, mean age 34.33 ± 12.34) were studied. The patients had a diagnosis of PFPS and no co-existent pathology. A system of markers was placed on anatomical landmarks on the lower limb and data was acquired using a 3 dimensional movement analysis system (CODA MPX30). Measurements were taken during 6 trials of single knee bends and squats. During the single leg knee bend test, subjects were asked to stand on one leg and flex their hip and knee as far as possible while maintaining their balance. The subjects also performed a full range squat. The maximum hip rotation angle around the longitudinal axis during single knee bends and squatting was measured. The data was analysed in Mathcad software and the kinematic data was time and amplitude normalized. Subsequently the hip rotation data was normalised to body height. Differences between groups were examined with a Mann Whitney test for non-parametric data. Reliability was studied on 2 healthy controls over 4 separate days. Results: Standard error of mean (SEM) for single knee bends and squats ranged from 0.21-0.72 and from 0.64-1.87 respectively for the 2 subjects over 4 days. The hip rotated internally during single knee bends in both healthy subjects and PFPS patients (7.99º ± 1.11 and 5.30º ± 2.85 respectively (mean ± SEM)). During squatting it rotated externally in both groups (22.90º ± 1.50 and 20.06º ± 4.20 respectively). No significant difference in hip rotation was noted between the two groups during either single knee bends (p= 0.49) or squatting (p= 0.68). There was no significant difference between healthy subjects and PFPS patients using the normalised hip rotation data (p= 0.42 on single knee bends and p= 0.47 on squats). Discussion: The reliability study demonstrated a consistent pattern and range of hip movement during a single leg stance and squat. As no significant differences were found between PFPS patients and healthy controls during a single knee bend and squatting, this study does not support the hypothesis that PFPS patients exhibit excessive internal rotation of the hip during dynamic activities. It has been reported that during single leg stance the pelvis shifts laterally over the weight bearing limb in order to ensure that the line of gravity falls within the base of support2. This results in an adduction moment occurring at the pelvis on the weight bearing limb and is considered to be a normal compensatory strategy. The results of this study suggest that the internal rotation of the hip demonstrated by most subjects during a single knee bend is a normal compensatory strategy for the alteration in base of support and the resultant effect on centre of gravity of this dynamic single-legged activity.