Altered Hip Flexor and Extensor Activation During Progressive Inclined Walking in Individuals With Femoroacetabular Impingement Syndrome.

Context: Femoroacetabular impingement syndrome (FAIS) is a movement-related condition associated with pain and impaired function; yet the evidence for level ground walking hip biomechanics is limited and inconsistent. Challenging the hip with inclined walking for individuals with FAIS might be important for elucidating mechanically driven function loss and informing tailored rehabilitation. The purpose of this study was to determine the effects of progressive inclined walking on sagittal hip biomechanics and hip flexor and extensor activity in individuals with FAIS.

Design: Cross-sectional.

Methods: Fourteen participants (7 individuals with FAIS and 7 asymptomatic individuals) underwent motion capture and electromyographic analysis during 3 treadmill walking conditions (0°/5°/10°). Statistical parametric mapping was used to compare the sagittal hip kinematic waveforms and hip flexor (rectus femoris) and extensor (gluteus maximus) waveforms between groups and walking conditions.

Results: Hip flexion was significantly increased throughout the gait cycle in individuals with FAIS compared with asymptomatic individuals (P < .01) but was not dependent on incline. Rectus femoris activation was significantly increased throughout stance in individuals with FAIS compared with asymptomatic individuals (P < .01). Gluteus maximus activity significantly increased with progressive inclination in asymptomatic individuals (P < .01), with no significant change in activity for individuals with FAIS.

Conclusions: Hip biomechanics and muscle activity during inclined walking mirrored that of arthrogenic muscle inhibition, highlighted by a prominent flexor role and lack of hip extensor activity in individuals with FAIS. Future research investigating discordant activity between hip flexors and extensors during complex functional tasks may help identify rehabilitation targets.