Lateral wedge insoles as a conservative treatment for pain in patients with medial knee osteoarthritis: a meta-analysis

Abstract

Importance: There is no consensus regarding the efficacy of lateral wedge insoles as a treatment for pain in medial knee osteoarthritis.

Objective: To evaluate whether lateral wedge insoles reduce pain in patients with medial knee osteoarthritis compared with an appropriate control.

Data sources: Databases searched include the Cochrane Central Register of Controlled Trials, EMBASE, AMED, MEDLINE, CINAHL Plus, ScienceDirect, SCOPUS, Web of Science, and BIOSIS from inception to May 2013, with no limits on study date or language. The metaRegister of Controlled Trials and the NHS Evidence website were also searched.

Study selection: Included were randomized trials comparing shoe-based treatments (lateral heel wedge insoles or shoes with variable stiffness soles) aimed at reducing medial knee load, with a neutral or no wedge control condition in patients with painful medial knee osteoarthritis. Studies must have included patient-reported pain as an outcome.

Data extraction and synthesis: Trial data were extracted independently by 2 researchers using a standardized form. Risk of bias was assessed using the Cochrane Risk of Bias tool by 2 observers. Eligible studies were pooled using a random-effects approach.

Main outcome and measures: Change in self-reported knee pain at follow-up.

Results: Twelve trials met inclusion criteria with a total of 885 participants of whom 502 received lateral wedge treatment. The pooled standardized mean difference (SMD) suggested a favorable association with lateral wedges compared with control (SMD, -0.47; 95% CI, -0.80 to -0.14); however, substantial heterogeneity was present (I2 = 82.7%). This effect size represents an effect of -2.12 points on the 20-point Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain scale. Larger trials with a lower risk of bias suggested a null association. Meta-regression analyses showed that higher effect sizes (unstandardized β, 1.07 [95% CI, 0.28 to 1.87] for trials using a no treatment control) were seen in trials using a no wedge treatment control group (n = 4 trials; SMD, -1.20 [95% CI, -2.09 to -0.30]) and lower effect sizes (unstandardized β, 0.26 [95% CI, 0.002 to 0.52] for each bias category deemed low risk) when the study method was deemed at low risk of bias. Among trials in which the control treatment was a neutral insole (n = 7), lateral wedges showed no association (SMD, -0.03 [95% CI, -0.18 to 0.12] on WOMAC; this represents an effect of -0.12 points), and results showed little heterogeneity (I2 = 7.1%).

Conclusions and relevance: Although meta-analytic pooling of all studies showed a statistically significant association between use of lateral wedges and lower pain in medial knee osteoarthritis, restriction of studies to those using a neutral insole comparator did not show a significant or clinically important association. These findings do not support the use of lateral wedges for this indication.

Figure 1

Review Flow Diagram

Figure 2. Forest Plot of Effect Size for Heel Wedge Interventions

Weights are from a random-effects analysis. SMD indicates standardized mean difference.