Effect of Biomechanical Footwear on Knee Pain in People With Knee Osteoarthritis: The BIOTOK Randomized Clinical Trial

Abstract

Importance: Individually calibrated biomechanical footwear therapy may improve pain and physical function in people with symptomatic knee osteoarthritis, but the benefits of this therapy are unclear.

Objective: To assess the effect of a biomechanical footwear therapy vs control footwear over 24 weeks of follow-up.

Design, setting, and participants: Randomized clinical trial conducted at a Swiss university hospital. Participants (N = 220) with symptomatic, radiologically confirmed knee osteoarthritis were recruited between April 20, 2015, and January 10, 2017. The last participant visit occurred on August 15, 2017.

Interventions: Participants were randomized to biomechanical footwear involving shoes with individually adjustable external convex pods attached to the outsole (n = 111) or to control footwear (n = 109) that had visible outsole pods that were not adjustable and did not create a convex walking surface.

Main outcomes and measures: The primary outcome was knee pain at 24 weeks of follow-up assessed with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscore standardized to range from 0 (no symptoms) to 10 (extreme symptoms). The secondary outcomes included WOMAC physical function and stiffness subscores and the WOMAC global score, all ranging from 0 (no symptoms) to 10 (extreme symptoms) at 24 weeks of follow-up, and serious adverse events.

Results: Among the 220 randomized participants (mean age, 65.2 years [SD, 9.3 years]; 104 women [47.3%]), 219 received the allocated treatment and 213 (96.8%) completed follow-up. At 24 weeks of follow-up, the mean standardized WOMAC pain subscore improved from 4.3 to 1.3 in the biomechanical footwear group and from 4.0 to 2.6 in the control footwear group (between-group difference in scores at 24 weeks of follow-up, -1.3 [95% CI, -1.8 to -0.9]; P < .001). The results were consistent for WOMAC physical function subscore (between-group difference, -1.1 [95% CI, -1.5 to -0.7]), WOMAC stiffness subscore (between-group difference, -1.4 [95% CI, -1.9 to -0.9]), and WOMAC global score (between-group difference, -1.2 [95% CI, -1.6 to -0.8]) at 24 weeks of follow-up. Three serious adverse events occurred in the biomechanical footwear group compared with 9 in the control footwear group (2.7% vs 8.3%, respectively); none were related to treatment.

Conclusions and relevance: Among participants with knee pain from osteoarthritis, use of biomechanical footwear compared with control footwear resulted in an improvement in pain at 24 weeks of follow-up that was statistically significant but of uncertain clinical importance. Further research would be needed to assess long-term efficacy and safety, as well as replication, before reaching conclusions about the clinical value of this device.

Trial registration: ClinicalTrials.gov Identifier: NCT02363712.

Figure 1.. Participant Recruitment, Randomization, and Follow-up

^aThe Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a self-administered questionnaire with a score range from 0 to 10 (0, no symptoms; 10, extreme symptoms). ^bThe Kellgren-Lawrence grade ranges from 0 to 4; a grade of 2 or greater indicates definite osteoarthritis on anteroposterior weight-bearing radiograph. ^cSTEADI indicates Stopping Elderly Accidents, Deaths, and Injuries; a score greater than 4 at the screening visit was considered to indicate a high risk of falls. The score range is 0 to 14. ^dOf the 7 participants in the biomedical footwear group and 13 participants in the control footwear group who discontinued treatment, 2 and 5, respectively, did not have data for the primary outcome and were counted as part of those who discontinued treatment. Multiple imputation was used for missing outcome data.

Figure 2.. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Scores During 24 Weeks of Follow-up

The box represents the median and interquartile range, the whiskers represent the most extreme values within 1.5 times of the interquartile range beyond the 25th and 75th percentile, and the circles represent the more extreme values. The WOMAC is a self-administered questionnaire including 5 questions on pain, 17 questions on physical function, and 2 questions on stiffness. All 4 composite scores were standardized to range from 0 to 10 (0, no symptoms; 10, extreme symptoms).