Varus Thrust Assessment Identified Responders to Quadriceps Exercise in Individuals at Risk of or with Knee Osteoarthritis.

Purpose: Identification of responders/nonresponders to unsupervised therapeutic exercise represents a critical challenge toward establishment of tailored self-management at home. Focusing on visualized varus thrust during gait as a possible effect moderator, this study determined whether and how varus thrust influences the therapeutic effects of home-based quadriceps exercise in individuals at increased risk of, or with, established knee osteoarthritis.

Methods: This study is a secondary subgroup analysis of a randomized controlled trial ( n = 50). Varus thrust at baseline was assessed via recorded gait movie. Analysis of covariance and subsequent mediation analysis were used to determine whether and how varus thrust influences the therapeutic effect of home-based quadriceps exercise after adjustment for covariates. To address the possible distinct impact of varus thrust on unsupervised and supervised exercise, the results were cross-checked with previous supervised exercise cohort using a meta-analysis.

Results: Individuals without varus thrust displayed greater and clinically meaningful pain relief after exercise after adjustment for covariates. The greater pain relief in individuals without varus thrust was attributed, at least partly, to an improvement in knee flexion range of motion. Notably, the meta-analysis revealed that unsupervised and supervised exercise programs induce consistent and clinically meaningful pain reduction in individuals without varus thrust.

Conclusions: Varus thrust is a robust effect moderator of the pain-reducing effect of quadriceps exercise. Furthermore, greater pain reduction may be a function of improvement of knee flexion range of motion. These studies provide evidence that varus thrust assessment represents valuable approach to identify responders/nonresponders to quadriceps exercise even for unsupervised protocol at their home environment.