Editorial Commentary: Bone Marrow Lesion as a Prognostic Factor for Osteochondral Allograft Transplantation of Cartilage Defects in the Knee Joint

Bone marrow lesions (BML) can be categorized as ischemic, mechanical, or reactive. BML are associated with cartilage loss and can be interpreted as a "stress-related bone marrow edema," and are a consequence of subchondral overload due to lack of cartilaginous cushioning and load distribution. The prevalence, depth, and cross-sectional area of BML increase with the degree cartilage defect. There is a risk that bone marrow edema will progress to subchondral cysts, and cysts are a point of no return of a BML. Thus, successful treatment of cartilage damage requires causally addressing the bone marrow edema, and it is also crucial for the therapy of the BML that cartilage damage is completely treated. A postoperative BML is associated with incomplete defect coverage due to incomplete ingrowth of the osteochondral allograft with missing closure of the cartilage surface, or insufficient containment. Ideal treatment for a circumscribed subchondral BML is a single cylinder replacing the damaged cartilage and the entire BML with an osteochondral allograft. In the case of larger defects or larger BML, successful treatment of the cartilage defect is the critical point.