Regional Trabecular Bone Alterations in Knee Osteoarthritis: QCT Evidence from the Knee and Lumbar Spine

Abstract Background Whether knee osteoarthritis (KOA)-related trabecular bone alterations are confined to the affected knee or also occur in the lumbar spine remains unclear. We compared regional knee and lumbar volumetric bone mineral density (vBMD) between KOA patients and non-KOA controls, examined lower-limb alignment relationships with medial–lateral tibial vBMD distribution, and compared bone metabolism markers between groups. Methods This single-centre cross-sectional study included 46 participants (32 KOA, 14 controls). Quantitative computed tomography (QCT) measured trabecular vBMD at the medial and lateral tibial plateaus (TM, TL), medial and lateral femoral condyles (FM, FL), and lumbar spine (LS); the hip–knee–ankle angle (HKA) was measured on weight-bearing full-length radiographs. vBMD–KOA associations were examined with Firth penalised-likelihood logistic regression adjusted for age, sex, and body mass index (BMI). Medial–lateral vBMD differences were assessed with paired Wilcoxon signed-rank tests, and between-group tibial vBMD distribution with a linear mixed-effects model. HKA–vBMD-difference associations used correlation and regression. Principal bone-metabolism markers (25-hydroxyvitamin D [25(OH)D], N-MID osteocalcin, β-CTX) were compared with false discovery rate (FDR) correction. Results After adjustment for age, sex, and BMI, each 1-SD increase in TM, TL, and LS vBMD was associated with adjusted odds ratios (ORs) for KOA of 0.34 (95% CI 0.11–0.80), 0.38 (0.13–0.98), and 0.53 (0.24–0.99), respectively; FM and FL showed no significant adjusted association. Within the KOA group, TM vBMD exceeded TL vBMD (P = 0.015), whereas the two were comparable in controls (P = 0.903); the group × compartment interaction was not significant (P = 0.259). HKA was smaller in KOA (P < 0.001); HKA–regional vBMD associations did not remain significant after correction. KOA also showed lower 25(OH)D and higher β-CTX (FDR q = 0.006 for both); adjusted ORs per 1-SD increase were 0.46 (0.19–0.88) and 2.97 (1.26–9.15). N-MID did not differ between groups. Conclusions KOA was associated with a region-specific pattern of lower trabecular vBMD, primarily involving both the medial and lateral tibial plateaus and the lumbar spine, alongside lower 25(OH)D levels. These findings suggest that KOA-related changes in bone mass are not confined to the affected knee and may reflect both localised bone remodelling and broader skeletal characteristics, providing a rationale for further longitudinal studies of regional QCT phenotypes.