Postoperative Articular Cartilage and Subchondral Bone Imaging

Magnetic resonance (MR) imaging plays an important role in the postoperative evaluation of cartilage repair procedures in the knee. MR imaging is the most reliable noninvasive method to assess cartilage repair tissue and underlying subchondral bone. Although the gold standard of evaluation is direct arthroscopic visualization and probing or histological examination of repair sites, MR affords an excellent noninvasive assessment of the repair site. MR has the added advantage of visualizing the subchondral bone that provides valuable information when planning treatment of symptomatic patients, especially in a revision surgery setting. MR also has the ability to demonstrate new joint pathology such as new cartilage defects elsewhere in the knee or meniscoligamentous pathology away from the repair site. To a degree, MR has reduced the need for second-look arthroscopy in clinical trials. The development of compositional MR techniques allows for evaluation of the microstructural and biochemical composition of the repair tissue and may serve as a surrogate for histological examination. Computed tomography (CT) arthrography is a complementary imaging test that provides excellent information about bone graft and subchondral bone. Although CT has relatively poor soft tissue contrast and cannot demonstrate bone marrow edema, CT arthrography can be a helpful alternative for patients who cannot undergo an MR imaging examination.