Lateral wedges in knee osteoarthritis: What are their immediate clinical and biomechanical effects and can these predict a three-month clinical outcome?

Objective. To assess immediate effects of laterally wedged insoles on walking pain, external knee adduction moment, and static, alignment, and whether these immediate effects together with age, body mass index, and disease severity predict clinical outcome after 3 months of wearing insoles in medial knee osteoarthritis. Methods. Forty volunteers (mean age 64.7 years, 16 men) were tested in random order with and without a pair of 5 degrees full-length lateral wedges. Immediate changes in static alignment were measured via radiographic mechanical axis and changes in adduction moment via 3-dimensional gait analysis. After 3 months of treatment with insoles, changes in pain and physical functioning were assessed via the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and patient-perceived global change scores. Results. Reductions in the adduction moment occurred with insoles (first peak mean [95% confidence intervals (95% CI)] -0.22 [0.28, -0.15] Nm/body weight x height %), accompanied by a reduction in walking pain of similar to 24% (mean [95% CI] -1.0 [-4.0, 2.0]). Insoles had no mean effect on static alignment. Mean improvement in WOMAC pain (P = 0.004) and physical functioning (mean [95% CI] -6 [-11, -1]) was observed at 3 months, with 25 (69%) and 26 (72%) of 36 individuals reporting global improvement in pain and functioning, respectively. Regression analyses demonstrated that disease severity, baseline functioning, and magnitude of immediate change in walking pain and the first peak adduction moment with insoles were predictive of clinical outcome at 3 months. Conclusion. Lateral wedges immediately reduced knee adduction moment and walking pain but had no effect on static alignment. Although some parameters predicted clinical outcome, these explained only one-third of the variance, suggesting that other unknown factors are also important.