Sex-Specific Associations of Radiographic Knee Osteoarthritis and Pain with Distal Tibia Bone Microarchitecture: the Study of Muscle, Mobility and Aging (SOMMA).

Knee osteoarthritis (OA) is the most common joint disease and despite being associated with higher areal bone mineral density (aBMD), increases fracture risk. This paradox suggests that in addition to mobility and fall concerns, microarchitectural deficits, not captured by DXA, may contribute to skeletal fragility in knee OA. This study aimed to examine cross-sectional associations of radiographic knee OA and knee pain with bone microarchitecture at the distal tibia and distal radius, assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT), in older adults. We studied 107 men and 159 women (age 77 ± 5 years) from the study of muscle, mobility and aging (SOMMA) who had knee radiographs and HR-pQCT scans. Radiographic knee OA was defined as Kellgren–Lawrence grade (KLG) 3–4, and knee pain was assessed using the Brief Pain Inventory questionnaire. Linear regression models estimated sex-specific associations of knee OA and pain with standardized HR-pQCT parameters, adjusting for age, BMI, FN aBMD, physical activity, fracture history, smoking, alcohol, and medication use. In women, at the distal tibia, radiographic knee OA was associated with lower cortical vBMD (B = − 0.55 SD, 95% CI − 0.91, − 0.20). In men, knee pain was associated with lower total and cortical vBMD, thinner cortices, and larger trabecular area. No associations were detected at the distal radius. Radiographic knee OA was more strongly associated with lower distal tibia cortical density in women, while pain was associated with overall structural and density deficits at distal tibia in men. These sex-specific patterns may inform fracture risk and OA etiology.