People with knee osteoarthritis who adopt a modified foot progression angle (FPA) during gait often benefit from a reduction in the knee adduction moment and knee pain. It is unknown, however, whether changes in the FPA increase hip moments, a surrogate measure of hip loading, which may increase the risk of hip pain or osteoarthritis. This study examined how altering the FPA affects hip moments. Individuals with knee osteoarthritis walked on an instrumented treadmill with their baseline gait, 10° toe-in gait, and 10° toe-out gait. A musculoskeletal modeling package was used to compute joint moments from the experimental data. Fifty participants were selected from a larger study who reduced their peak knee adduction moment with a modified FPA. In this group, participants reduced the first peak of the knee adduction moment by 7.6% with 10° toe-in gait and reduced the second peak by 11.0% with 10 ° toe-out gait. Modifying the FPA reduced the early-stance hip abduction moment, at the time of peak hip contact force, by 4.3% ± 1.3% for 10° toe-in gait (p=0.005) and by 4.6% ± 1.1% for 10° toe-out gait (p<0.001) without increasing the flexion and internal rotation moments (p>0.15). In summary, when adopting a FPA modification that reduced the knee adduction moment, participants did not increase surrogate measures of hip loading.
Foot progression angle and the knee adduction moment: a cross-sectional investigation in knee osteoarthritis
