In uncontrolled studies, a lateral-wedge insole has reduced knee pain in patients with medial knee osteoarthritis (OA). The aim of this study was to test the efficacy of this simple, low-cost intervention for pain in patients with medial knee OA.
We conducted a double-blind, randomized, crossover trial designed to detect a small effect of treatment. Participants were at least 50 years of age and had medial joint space narrowing on posteroanterior semiflexed radiographs and scores indicating moderate pain for 2 of the 5 items on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scale. Participants were randomized to receive a 5 degrees lateral-wedge insole or a neutral insole for 6 weeks. Following a 4-week washout period, participants crossed over to the other treatment for 6 weeks. Knee pain, the primary outcome, was assessed by the WOMAC pain scale (visual analog scale version). Secondary outcomes included the WOMAC disability subscale, overall knee pain, 50-feet walk time, chair-stand time, and use of medications for knee pain.
Ninety patients were randomized. The mean difference in pain between the 2 treatments was 13.8 points on the WOMAC pain scale (95% confidence interval -3.9, 31.4 [P=0.13]). We observed similar small effects for the secondary outcomes.
The effect of treatment with a lateral-wedge insole for knee OA was neither statistically significant nor clinically important.