Osteoarthritis (OA) is a debilitating disease marked by changes in cartilage and subchondral bone, but symptomatically marked by pain. Pain pathophysiology is poorly understood, but as patellar subchondral bone is innervated, it could be linked to OA-related knee pain. Also, subchondral cortical and trabecular bone may each play individual roles in OA-related pain pathophysiology.

The overall goal of this study was to determine how subchondral bone is related to pain in OA. The objectives of this study were 1) to measure to in vivo precision of computed tomography topographic mapping of subchondral density (CT-TOMASD) in the patella, and to 2) to apply CT-TOMASD to a clinical sample to determine if there were differences in patellar subchondral bone density between knee OA patients with different pain experiences.

In vivo precision (CV%RMS) of CT-TOMSAD in the patella ranged from 1.1% to 6.8%. Precision errors were approximately 4 times greater than observed BMD differences between healthy and OA groups.

In the clinical analysis, participants with ‗severe pain at rest‘ had 16% lower BMD over the total lateral patellar facet at depths of 5-7.5mm from the subchondral surface than participants with ‗non-severe pain at rest‘. Regional analysis showed that participants with ‗severe pain at rest‘ had lower BMD in the inferior lateral facet;​ 13% at the 0-2.5mm depth, 23% at the 2.5-5mm depth, and 22% at the 5-7.5mm depth.

This is the first study to report QCT-based subchondral cortical and trabecular BMD values in the patella. This is also the first application of CT-TOMASD to a sample of participants with clinically diagnosed OA;​ and the first study to report relationships between BMD and pain, showing that trabecular bone changes may be related to pain.