Associations between systemic bone mineral density and early knee cartilage changes in people without clinical knee disease

Purpose: It has been speculated that osteoarthritis (OA) is more prevalent in people with a high bone mineral density (BMD). Nevertheless, whether a high systemic BMD predates early structural features of knee OA is unclear. This study examined the association between systemic BMD and cartilage volume loss and cartilage defect progression over 2 years. Methods: 153 participants with no significant musculoskeletal disease were recruited from local media and weight-loss clinics (mean BMI 32.3 kgm-2). Femoral neck and total body BMD was assessed via Dual-energy X-ray absorptiometry at baseline (2005–2008), and knee cartilage volume and defects by magnetic resonance imaging at baseline and follow-up (2008–2010). Results: Greater baseline total BMD was associated with increased cartilage volume loss (3.7%/annum, 95% CI 1.1% to 6.3%, for one g cm-2 higher BMD) and a trend towards progression of tibiofemoral cartilage defects (OR 1.05, 95% CI 1.00 to 1.10 for one g/100cm2 increase in BMD). Significant results were found in the lateral but not the medial knee compartment. For instance, for every one g cm-2 increase in total BMD, there was a 5.2% (95% CI 2.2–8.3%) increase in lateral tibial cartilage volume loss. Similar relationships were apparent for femoral neck BMD. Conclusions: In people without clinical knee disease, higher baseline systemic BMD was associated with increased loss of cartilage volume and progression of cartilage defects in the lateral knee. Further work in this area will be important, particularly given the current interest in therapies targeting bone as potential disease modifying OA drugs.