Dual-energy X-ray absorptiometry applied to the assessment of tibial subchondral bone mineral density in osteoarthritis of the knee

Objective: Plain X-ray is an imprecise tool for monitoring the subchondral bony changes associated with the development of knee osteoarthritis (OA). Our objective was to develop and validate a technique for assessing tibial subchondral bone density (BMD) in knee OA using dual energy X-ray absorptiometry (DXA). Design: Patients with OA of at least one knee underwent DXA scanning of both knees. Regions of interest (ROI) were placed in the lateral and medial compartments of tibial subchondral bone. Weight-bearing plain X-rays and Te-99m scintiscans of both knees were obtained and scored. Results: One hundred and twelve patients (223 knees) underwent DXA and radiography. Intra-observer CV% was 2.4% and 1.0% for the medial and lateral ROI respectively. Definite OA (Kellgren and Lawrence Grade 2, 3 or 4) was correlated with age-related preservation of subchondral BMD compared to radiographically normal knees. Raised BMD was also associated with subchondral sclerosis, and positive scintigraphy. Conclusion: DXA may provide a safe, rapid and reliable means of assessing knee OA. Cross-sectional age-related subchondral tibial BMD loss is attenuated by knee OA.