Effects of Chondroitin Sulfate on Joint Symptoms and Physical Function in Adults with Mild Knee Osteoarthritis: A Randomized, Double-Blind, Placebo-Controlled Trial

Background/Objectives: Although chondroitin sulfate (CS) is commonly used for knee osteoarthritis (OA), evidence regarding its effects on joint symptoms and physical function remains inconsistent. This study aimed to evaluate the effects of CS supplementation on joint symptoms and physical function in adults with mild knee OA. Methods: In this 12-week, randomized, double-blind, placebo-controlled trial, 100 adults with mild knee OA were randomly assigned to receive CS (1200 mg/day; n = 50) or placebo (n = 50). The primary outcomes were the Korean Western Ontario and McMaster Universities Osteoarthritis Index (K-WOMAC) total and subscale scores. Secondary outcomes comprised the pain visual analog scale (VAS), 20-m walking time, Korean Australian/Canadian Osteoarthritis Hand Index (K-AUSCAN), and grip and pinch strength. Results: At week 12, the reduction in the K-WOMAC total score was significantly greater with CS than with placebo (−19.26 ± 2.74 vs. −2.10 ± 1.37; p < 0.001), along with greater reductions in the pain, stiffness, and physical function subscale scores (all p < 0.001). Notable improvements were also observed in the pain VAS (−18.82 ± 3.50 vs. −3.04 ± 3.10 mm) and 20-m walking time (−1.40 ± 0.62 vs. 0.23 ± 0.32 s) (both p < 0.001). K-AUSCAN scores and grip and pinch strength also improved significantly compared to placebo. No clinically meaningful safety concerns were observed. Conclusions: These findings suggest that CS supplementation may be beneficial in improving joint symptoms and physical function in adults with mild knee OA, demonstrating consistent benefits across both self-reported outcomes and objective walking performance.