Sagittal plane hip motion reversals during walking are associated with disease severity and poorer function in subjects with hip osteoarthritis

A midstance reversal of sagittal plane hip motion during walking, or motion discontinuity (MD), has previously been observed in subjects with endstage hip osteoarthritis (OA) and in patients with femoroacetabular impingement. The goal of the present study was to evaluate whether this gait pattern is a marker of OA presence or radiographic severity by analyzing a large IRB approved motion analysis data repository. We also hypothesized that subjects with the MD would show more substantial gait impairments than those with normal hip motion. We identified 150 subjects with symptomatic unilateral hip OA and Kellgren–Lawrence OA severity data on file, and a control group of 159 asymptomatic subjects whose ages fell within 2 standard deviations of the mean OA group age. From the gait data, the MD was defined as a reversal in the slope of the hip flexion angle curve during midstance. Logistic regressions and general linear models were used to test the association between the MD and OA presence, OA severity and, other gait variables. 53% of OA subjects compared to 7.5% of controls had the MD (p<0.001); occurrence of the MD was associated with OA severity (p=0.009). Within the OA subject group, subjects with the MD had reduced dynamic range of motion, peak, extension, and internal rotation moments compared to those who did not (MANCOVA p≤0.042) after controlling for walking speed. We concluded that sagittal plane motion reversals are indeed associated with OA presence and severity, and with more severe gait abnormalities in subjects with hip OA.