Usefulness of 3D joint space width on weight-bearing CT in comparison with 2D joint space width on radiographs for predicting 24-month worsening of knee osteoarthritis pain and function in the MOST study.

OBJECTIVE: This study compared the predictive validity of three-dimensional joint space width (3D-JSW) on weight-bearing computed tomography (WBCT) versus two-dimensional joint space width at predetermined mediolateral locations (2D-JSWx) on radiographs for worsening knee pain and physical function over 24 months. DESIGN: Data from 302 participants (425 knees) in the Multicenter Osteoarthritis Study (MOST) were analyzed. Baseline assessments included bilateral standing radiographs for 2D-JSWx and WBCT for 3D-JSW. Minimal clinically important worsening (MCIW) of pain (Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale) and function (20-m walk, sit-to-stand, WOMAC function subscale) over 24 months was assessed. Logistic regression with generalized estimating equations (GEE) accounted for within-person correlation, and predictive validity was evaluated by comparing receiver operating characteristic (ROC) areas under the curves (AUC). RESULTS: Participants had a mean age of 63.2±8.9 years and body mass index (BMI) of 28.2±4.8 kg/m². Over 24 months, 38 knees exhibited worsening WOMAC pain, with no significant association for either 3D-JSW or 2D-JSWx. For WOMAC pain, 3D-JSW (AUC=0.578) was not superior to 2D-JSWx (AUC=0.511; difference: 0.067 (95% confidence interval (CI): -0.040, 0.175)). Similar results were noted for the 20-m walk (difference: 0.003 (95% CI: -0.049, 0.055)), sit-to-stand test (difference: 0.014 (95% CI: -0.034, 0.062)), and WOMAC function (difference: -0.020 (95% CI: -0.091, 0.050)). CONCLUSIONS: 3D-JSW on WBCT did not outperform 2D-JSWx on radiography for predicting knee pain and functional worsening. However, WBCT offers several advantages, including improved imaging capabilities, that may facilitate assessment of osteoarthritis in clinical practice and research.