Introduction Subchondral bone attrition (SBA), a feature of osteoarthritis, may be caused by excess focal load to bone, and/or inadequate bone quality to withstand loads through the joint. This study 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 Study is a cohort of individuals who have or are at high risk of knee osteoarthritis. Baseline alignment and bone mineral density (BMD) measures were assessed. Baseline and 30-month knee magnetic resonance images were graded for SBA (grade 0–3) using the whole-organ magnetic resonance imaging score. The study 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 body mass index.
Results Of 1253 participants (mean age 62 years, mean BMI 30, 61% women), 33% had baseline SBA and 44% had knee osteoarthritis. Associations between the presence and incidence of SBA with malalignment in both compartments were noted (odds ratios (95% CI) 2.9 (2.1 to 4.0) and 1.9 (1.2 to 2.9), respectively, for varus knees in the medial compartment; 4.5 (2.8 to 7.1) and 2.1 (1.1 to 4.1), respectively, for valgus knees in the lateral compartment). Low BMD was not associated with SBA.
Conclusions The 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 contribute to increased forces transmitted to the cartilage due to alteration in subchondral bone.
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Funding National Institutes of Health (NIH) grants for MOST from NIA: DF (U01 AG18820), JT (U01 AG18832), CEL (U01 AG18947), MN (U01 AG19069). LS: R01 HD43502; TN was supported by the following during the course of this work: Arthritis Foundation Arthritis Investigator Award, ACR-REF/ASP Junior Career Development Award in Geriatrics (T Franklin Williams Scholar Award), NIAMS K23 AR055127; NIH AR47885. The sponsors had no role in the study design, collection, analysis and interpretation of data, in writing of the report and in the decision to submit the paper for publication.
Competing interests None.
Ethics approval This study was conducted with the approval of the institutional review boards at the University of Iowa, University of Alabama, Birmingham, University of California, San Francisco and Boston University Medical Center.
Provenance and peer review Not commissioned; externally peer reviewed.