Objective: To compare the clinical effects of laterally wedged insoles and neutrally wedged insoles (used as control) in patients with medial femoro-tibial knee osteoarthritis.
Study design: 24-month prospective randomized controlled study.
Patients: Outpatients with painful medial femoro-tibial knee osteoarthritis.
Outcome measures: Patient's overall assessment of disease activity (5 grade scale), WOMAC index subscales and concomitant treatments.
Statistical analysis: Performed as an intention-to-treat analysis, with the last observation carried forward (LOCF). Main symptomatic criterion: Improvement in the patient's assessment of activity (defined as a reduction of one grade or more at the end of the study as compared to baseline, and no intra-articular injection or lavage during the 6 months previous to the last visit). Secondary criteria for assessment: (a) Changes in the WOMAC subscales at month 24, and (b) concomitant therapies (analgesics, NSAIDs and intra-articular injections or lavages). Structural criterion: Joint space width (JSW) at the narrowest point. Non-compliance was defined as intermittent or lack of insole fitting at two consecutive visits. Compliance within groups was compared by using a life table analysis technique (Log-Rank).
Results: The baseline characteristics of the 156 recruited patients (41 males, 115 females, mean age 64.8 years) were not different in the 2 treatment groups. At year 2, there was no statistically significant difference between the 2 groups concerning the percentages of patients with improvement in both global assessment of disease activity and in WOMAC subscales (pain, stiffness, function). The number of days with NSAIDs intake was lower in the group with laterally wedged insoles than in the neutrally wedged group (71+/-173 days vs. 127+/-193 days, P=0.003, Mann-Whitney test). The mean joint space narrowing rate did not differ between the two groups: 0.21+/-0.59 mm/year in the laterally wedged group vs 0.12+/-0.32 mm/year in the neutrally wedged group. Compliance and tolerance were satisfactory. Compliance was different between the 2 groups at month 24, with a greater frequency of patients who wore insoles permanently in the laterally wedged insole group than in the other group (85.8% vs 71.9%, P=0.023).
Conclusion: This study failed to demonstrate a relevant symptomatic and/or structural effect of laterally-wedged insoles in medial femoro-tibial OA. However, the reduced NSAIDs intake and the better compliance in the treatment group are in favor of a beneficial effect of laterally-wedged insoles in medial femoro-tibial OA.