Introduction: Subchondral bone attrition (SBA), a feature of OA, may be caused by excess focal load to bone, and/or inadequate bone quality to withstand loads through the joint. We evaluated the effects of malalignment, which can cause focal excessive load, and systemic bone density on the presence and incidence of SBA.
Methods: The Multicenter Osteoarthritis (MOST) Study is a cohort of individuals who have or are at high risk for knee OA. Baseline alignment and BMD measures were assessed. Baseline and 30-month knee MRIs were graded for SBA (grade 0-3) using WORMS. We evaluated the association of alignment in medial and lateral compartments, respectively, and systemic BMD with baseline presence of SBA and incident SBA using logistic regression and adjusting for age, sex, and BMI.
Results: There were 1253 participants with mean age 62, mean BMI 30 and 61% were female. 33% had baseline SBA and 44% had knee OA. Associations between presence of and incident SBA with malalignment in both compartments were noted (ORs (95% CI) 2.9 (2.1-4.0) and 1.9 (1.2-2.9), respectively, for varus knees in the medial compartment; 4.5 (2.8-7.1) and 2.1 (1.1-4.1), respectively, for valgus knees in the lateral compartment). Low BMD was not associated with SBA.
Conclusions: Presence and incidence of SBA are associated with malalignment in a compartment-specific manner, but not with low BMD. SBA may be a marker of increased load experienced by overlying cartilage, which may in turn contribute to increased forces transmitted to the cartilage due to alteration in subchondral bone.