The immediate effects of passive hip joint mobilization on hip abductor/external rotator muscle strength in patients with anterior knee pain and impaired hip function. A randomized, placebo-controlled crossover trial

Background: Anterior knee pain (AKP) is often associated with persistent hip muscle weakness and facilitatory interventions may be beneficial for managing patients with AKP (pwAKP). Physiotherapists often employ passive oscillatory hip joint mobilizations to increase hip muscle function. However, there is little information about their effectiveness and the mechanisms of action involved. Objectives: To investigate the immediate effects of passive hip joint mobilization on eccentric hip abductor/external rotator muscle strength in pwAKP with impaired hip function. Design A double-blinded, randomized, placebo-controlled crossover design. Method Eighteen patients with AKP participated in two sessions of data collection with one week apart. They received passive hip joint mobilization or placebo mobilization in a randomized order. Eccentric hip muscle strength was measured immediately before and after each intervention using a portable hand-held dynamometer. Results: An ANCOVA with the sequence of treatment condition as the independent variable, the within-subject post-treatment differences as the dependent variable and the within-subject pre-treatment differences as the covariate was conducted. Patients showed a significant mean increase in eccentric hip muscle strength of 7.73% (p = 0.001) for the mobilization condition, compared to a mean decrease of 4.22% for the placebo condition. Seventeen out of eighteen participants reported having no pain during any of the strength testing. Conclusion: These data suggest that passive hip joint mobilization has an immediate positive effect on eccentric hip abductor/external rotator muscle strength in pwAKP with impaired hip function, even in the absence of current pain.