Surgical treatments of bone marrow lesions.

Bone marrow lesions (BMLs) of the knee are a common magnetic resonance imaging finding, defined as an alteration of the bone marrow detectable as a high signal on fluid-sensitive sequences. A wide range of pathologies can present with BMLs, including traumatic lesions, osteoarthritis, subchondral insufficiency fractures and osteonecrosis. Several treatment options have been proposed to address BML, from conservative to surgical approaches. If nonoperative treatments fail, operative treatments are indicated. These procedures include intraosseous injections, unloading procedures and meniscus implants. In detail, intraosseous injections may be performed with biomaterials like calcium phosphate, or with orthobiologics like platelet-rich plasma or mesenchymal stromal cells. Aim of these interventions is either to stabilise the microtrabecular tissue or to promote a healing response. Good results have been reported in the literature for many of the available surgical options, but the level of evidence is still suboptimal, and the best approach has not yet been identified. Level of Evidence: Level V, expert opinion.