The Cartilage Thickness Score (CTh-Score) detects a structural effect of 2-year weight loss: data from the Osteoarthritis Initiative

Objective To determine whether clinically significant weight loss ([&ge;]5% of body weight) is associated with slower 2-year knee cartilage structural deterioration, using the Cartilage Thickness Score (CTh-Score). Method A retrospective propensity-score-matched cohort study was conducted using Osteoarthritis Initiative study data. Weight loss was defined as [&ge;]5%; stable weight as <5% loss and <5% gain. Cases were matched 1:2 to controls using age, sex, body mass index, visit, Kellgren Lawrence grade, KOOS Pain, and physical activity. The primary outcome was change in CTh-Score, a 0-100 cartilage structural assessment score derived from the spatial distribution of cartilage thickness, with higher scores indicating greater severity. Secondary outcomes were KOOS Pain and conventional structural metrics: minimum medial joint space width and mean cartilage thickness in four femoral/tibial regions. Linear regression with matched-set cluster-robust standard errors estimated crude and adjusted differences with 95% confidence intervals (CIs). Results A total of 643 weight-loss participants were matched to 1,286 stable-weight controls; all absolute standardized mean differences were <0.10. Weight loss participants experienced less CTh-Score progression over two years than stable-weight controls (mean change 2.71 (SD 6.85) versus 4.29 (8.00), respectively). The adjusted between-group difference (weight loss minus stable weight) was -1.59 (95% CI -2.29 to -0.89; p<0.001; Cohen's d=-0.21). There was no evidence that the association differed by radiographic osteoarthritis status (p=0.261). No statistically significant adjusted differences were found for minimum joint space width or regional mean cartilage thickness. The adjusted KOOS Pain difference was 1.14 points (95% CI -0.08 to 2.35; p=0.070). Conclusions Clinically significant weight loss was associated with slower knee cartilage structural progression over 2 years when assessed using the CTh-Score, despite no detectable differences in conventional structural measures. These findings suggest that weight management is associated with more favorable cartilage structural outcomes and highlight the CTh-Score as a sensitive endpoint for detecting structural change.