Weight-bearing CT imaging of the lower limb: lessons learned and future opportunities from the multicenter osteoarthritis study (MOST).

Objective

To summarize findings from weight-bearing computed tomography (WBCT) studies within the Multicenter Osteoarthritis Study (MOST) and discuss lessons learned and highlight their potential for improving understanding osteoarthritis (OA) structural progression.

Design

Narrative review of WBCT studies within MOST, a multicenter longitudinal prospective cohort study. WBCT of bilateral knees was acquired for 824 participants during the third cycle (MOST3; 2015-2020), and bilateral hips, knees, and feet/ankles in 1647 participants during the fourth cycle (MOST4; 2023-2028).

Results

MOST3 established that WBCT-derived tibiofemoral 3D joint space width (JSW) is highly reproducible (ICC=0.90-0.97) and strongly correlated with radiographic JSW (r = 0.91-0.97), although radiographs overestimated JSW by ∼2 mm. Medial tibiofemoral JSW on WBCT correlated more strongly with cartilage/meniscal morphology on MRI than radiographic JSW, and 3D JSW was more responsive to 2-year structural change than radiographic JSW. WBCT more sensitively detected patellofemoral cartilage abnormalities, osteophytes, subchondral cysts, and meniscal extrusion than radiographs and non-weight-bearing MRI. CT OA of the Knee Score (COAKS) demonstrated substantial reliability (weighted κ=0.66-0.87; ICC >0.81), and a bone-shape C-score predicted two-year worsening of knee pain in women and structural worsening in men. Narrower 3D JSW was associated with worse physical function.

Conclusions

WBCT provides a reliable, physiologically-loaded 3D joint assessment that is more sensitive and responsive than radiographs, with practical advantages over MRI and MDCT in acquisition time, radiation dose, and infrastructure. These properties support its clinical potential for earlier OA detection in lower limb OA phenotyping and structural progression monitoring. MOST4 offers opportunities to validate WBCT imaging biomarkers across the lower limb kinetic chain.