Effect of variable‐stiffness walking shoes on knee adduction moment, pain, and function in subjects with medial compartment knee osteoarthritis after 1 year

This study investigated the load‐modifying and clinical efficacy of variable‐stiffness shoes after 12 months in subjects with medial compartment knee osteoarthritis. Subjects who completed a prior 6‐month study were asked to wear their assigned constant‐stiffness control or variable‐stiffness intervention shoes during the remainder of the study. Changes in peak knee adduction moment, total Western Ontario and McMaster Universities (WOMAC), and WOMAC pain scores were assessed. Seventy‐nine subjects were enrolled, and 55 completed the trial. Using an intention‐to‐treat analysis, the variable‐stiffness shoes reduced the within‐day peak knee adduction moment (−5.5%, p < 0.001) in the intervention subjects, while the constant‐stiffness shoes increased the peak knee adduction moment in the control subjects (+3.1%, p = 0.015) at the 12‐month visit. WOMAC pain and total scores for the intervention group were significantly reduced from baseline to 12 months (−32%, p = 0.002 and −35%, p = 0.007, respectively). The control group had a reduction of 27% in WOMAC pain score (p = 0.04) and no significant reduction in total WOMAC score. Reductions in WOMAC pain and total scores were similar between groups (p = 0.8 and p = 0.47, respectively). In the intervention group, reductions in adduction moment were related to improvements in pain and function (R² = 0.11, p = 0.04). Analysis by disease severity revealed greater efficacy in adduction moment reduction in the less severe intervention group. While the long‐term effects of the intervention shoes on pain and function did not differ from control, the data suggest wearing the intervention shoe reduces the within‐day adduction moment after long‐term wear, and thus should reduce loading on the affected medial compartment of the knee.