Disease severity affects knee range of motion but not strength deficits in knee osteoarthritis

Objectives: To compare knee range of motion and muscle strength between individuals with symptomatic knee osteoarthritis and healthy controls, and to assess how Kellgren–Lawrence grade and measurement protocols affect these outcomes.Methods: A systematic search of PubMed, Scopus, and Web of Science identified studies comparing knee flexion/extension range of motion or flexor/extensor strength between patients with knee osteoarthritis and controls. Risk of bias was assessed with Joanna Briggs Institute tools. Pooled mean and standardized mean differences with 95% confidence intervals were calculated using random-effects meta-analyses.Results: Thirty studies were included. Compared with healthy controls, individuals with knee osteoarthritis showed significantly reduced knee flexion [MD = 16.30°, 95%CI (11.40, 21.21)] and extension [MD = 4.25°, 95%CI (2.30, 6.19)], with greater flexion loss in advanced KL grades. Knee osteoarthritis participants also demonstrated significantly lower strength across all contraction types: isometric [extensors: SMD = 0.86, 95%CI (0.57, 1.14)