Bone marrow lesions (BMLs) are a hallmark sign of osteoarthritis (OA) associated with clinical symptoms of pain and pain progression. Based on previous literature, BMLs are likely centers of increased bone remodeling. Currently, there is no consensus as to what defines a BML outside of its appearance on MRI. This study aimed to better understand bone remodeling rates in BML tissue versus matched OA control tissue from total knee arthroplasty (TKA) tibial plateau explants in five individuals with end stage OA.

Participants were scanned with magnetic resonance imaging (MRI) six months prior to TKA. Tetracycline hydrochloride was administered to produce fluorescent double labels signifying newly mineralized bone. BMLs and paired control (BML-free) regions were identified in the tibial plateaus on the in vivo MRI images before polymethyl methacrylate embedding and sectioning. BIOQUANTOsteo and paired T tests were used to measure differences in mineral appositional rate (MAR), bone formation rate (BFR/BS), and mineralizing surface (MS/BS) on histological sections.

Five tibial plateau explants showed that MAR was significantly higher in the BML group (1.14 +/- 0.3µm/day) than the control group (0.37 +/- 0.24µm/day, p = 0.0003). BFR/BS (p = 0.058) and MS/BS (p = 0.140) appeared to trend higher in the BML group (0.08 +/- 0.07µm/day, 0.064 +/- 0.046%, respectively) than in the paired control group (0.02 +/- 0.02µm/day, 0.042 +/- 0.039%, respectively). Taken together these results signify that BMLs likely have an increased rate of bone remodeling when compared to paired non BML OA tissue.

This research could assist in elucidating novel therapeutic targets for treatment of knee OA and identify those needing TKA, thus improving the quality of life for affected individuals.