Purpose: Previous research had found that an increased hip adduction moment during walking was protective of knee osteoarthritis (OA) progression (based on radiographic medial joint space grading). It is speculated that this is due to stronger hip abductor muscles which help stabilize the pelvis on the stance limb and prevent pelvic drop of the swing limb. If the hip abductors of the stance limb are weak, the pelvis may drop towards the contralateral swing limb resulting in a shift of the centre of mass away from the stance limb, thereby increasing the frontal plane lever arm at the knee and subsequently increasing the peak knee adduction moment, a proxy for medial compartment loading. The purposes of this study were to examine the relationship between baseline a) hip adduction moment and b) hip abductor strength, and changes in cartilage morphology over 12 months in people with medial knee OA. Methods: 200 individuals with medial knee OA were recruited for a clinical trial evaluating the efficacy of lateral wedge insoles on slowing structural disease progression. Since the wedges had no effect on symptoms or structural changes, data from 144 participants (71 lateral wedge insoles, 73 control insoles; 72% of participants) who completed a three-dimensional gait analysis, as well as baseline and follow-up MRIs, were pooled for the current study. A subset of participants from the control insoles group (n = 49) also underwent hip abductor strength testing at baseline. Sagittal MR knee images were obtained on a 1.5-T whole body unit. Annual change in tibial cartilage volume was determined by subtracting the follow-up volume from baseline volume and dividing by time between scans. Progression of cartilage defects and bone marrow lesions (BMLs) was determined by subtracting the cartilage defect/BML grade at follow-up from that at baseline. A value less than or equal to -1 represented progression. A multiple linear regression model was used to examine the relationship between hip adduction moment (independent variable) and annual change in medial tibial cartilage volume (dependent variable). Binary logistic regressions were used to examine the association between hip adduction moment (independent variable) and progression of tibiofemoral cartilage defects and BMLs (dichotomized dependent variables). Analyses were repeated using hip abductor strength as the independent variable. All models were initially adjusted for age, sex, body mass index and repeated with additional covariates of intervention group, MRI machine and alignment. Results: Baseline hip adduction moment during walking and hip abductor strength were not associated with either change in medial tibial cartilage volume or progression of medial tibiofemoral cartilage defects or BMLs (Table 1). (Table presented) Conclusions: These findings suggest that neither an increased hip adduction moment nor increased hip abductor strength is protective against change in cartilage volume/morphology in medial knee OA. These findings are consistent with recent hip strengthening intervention studies which have found that increased hip abductor strength does not alter the knee adduction moment.
Kean, C. O., Bennell, K. L., Bowles, K., & Hinman, R. S. (2011). 94 RELATIONSHIP BETWEEN HIP ADDUCTION MOMENT, HIP ABDUCTOR STRENGTH AND PROGRESSION OF KNEE OSTEOARTHRITIS. Osteoarthritis and Cartilage, 19, S49. https://doi.org/10.1016/s1063-4584(11)60121-0