Toe-out, lateral trunk lean, and pelvic obliquity during prolonged walking in patients with medial compartment knee osteoarthritis and healthy controls

Objective To compare the time-varying behavior of maximum toe-out angle, lateral trunk lean (over the stance leg), and pelvic obliquity (rise and drop on the swing leg) during prolonged walking in participants with and without medial compartment knee osteoarthritis (OA), and to explore correlations between these gait characteristics and pain. Methods. Twenty patients with knee OA and 20 healthy controls completed 30 minutes of treadmill walking. Toe-out, trunk lean, pelvic obliquity, and pain were measured at 5-minute intervals. Results. The mean +/- SD toe-out angle was significantly smaller (P = 0.04) in patients with knee OA (6.7 +/- 2.5 degrees) than in controls (10.3 +/- 2.2 degrees). Toe-out changed significantly over time (P = 0.002), but not in a systematic way, and there was no interaction between group and time. The mean +/- SD trunk lean was higher (P = 0.03) in patients with knee OA (2.0 +/- 1.0 degrees) than in controls (0.7 +/- 0.5 degrees). Trunk lean did not change over time and there was no interaction between group and time. There were no differences for pelvic drop. The mean +/- SD pelvic rise was higher (P +/- 0.01) in patients with knee OA (2.8 +/- 0.9 degrees) than in controls (1.2 +/- 0.8 degrees), but did not change over time and there was no interaction. Patients experienced a small increase in pain (P < 0.001). Trunk lean and pelvic drop were correlated with pain (r = 0.49, P = 0.03 and r = 0.47, P = 0.04, respectively). Conclusion. Toe-out and trunk lean are consistently different between individuals with and without medial compartment knee OA during prolonged walking, and patients with greater pain have greater trunk lean. However, over 30 minutes of walking, these gait characteristics remain quite stable, suggesting they are not acute compensatory mechanisms in response to repetitive loading with subtle increases in pain.