Repeatability of objective bone and joint measures in the knee using weight-bearing computed tomography: three-dimensional quantification of bone mineral density, joint space width, and subchondral bone plate thickness.

Bone alterations and degenerative joint structural changes are frequently observed in knee osteoarthritis (OA). Objective measures of subchondral bone plate thickness (SBP.Th), apparent BMD, and joint space width (JSW) have begun to be used to better assess and understand disease progression. Weight-bearing CT (WBCT) allows 3D assessment of multiple bone and joint parameters; however, there is a paucity of literature investigating factors that might affect our ability to track changes over time. The purpose of this study was to investigate the repeatability of BMD, JSW, and SBP.Th measures obtained from WBCT images. Same-day, scan-rescan, knee WBCT images were acquired from 37 healthy adults (20 female, mean age: 24.6 yr). We quantified trabecular bone BMD at the proximal tibia and implemented joint space and cortical bone mapping to measure tibiofemoral JSW and SBP.Th, respectively. Test-retest repeatability was evaluated using coefficients of variation (CVRMS%) and least significant change (LSC). Mean trabecular BMD exhibited CVRMS% ranging from 1.87% to 2.85% and LSCs between 13.53 and 17.39 mgHA/cm3. For JSW, CVRMS% and LSC were less than 1% and 0.2 mm, respectively. SBP.Th measures had higher CVRMS% (9.75%-11.29%) but similar LSC values (0.09-0.26 mm) in comparison to JSW values. The high repeatability of subchondral bone and joint parameters underscore the potential of WBCT for quantifying and monitoring bone and joint changes in knee OA progression and management. However, standardization of acquisition and analysis methods will likely be required to ensure reliable evaluation over multiple time points.