Clinical and Pathophysiologic Significance of MRI Identified Bone Marrow Lesions Associated with Knee Osteoarthritis.

Knee osteoarthritis (OA) affects the joint beyond just the articular cartilage. Specifically, magnetic resonance imaging-identified bone marrow lesions (BML) in the subchondral bone have both clinical and pathophysiological significance. Compared to joint space narrowing on traditional radiographs, the presence of BMLs has been better correlated with severity of clinical symptoms as well as clinical deterioration. Presence of a BML increases the likelihood for progression to a total knee arthroplasty by up to nine fold. Histochemical analysis of BMLs has shown increased levels of tumor necrosis factor-alpha, matrix metalloproteinases and substance P, thought to stimulate pain receptors in osteoarthritis. LEVEL OF EVIDENCE: V.