Bone Marrow Edema in the Knee and Its Influence on Clinical Outcome After Matrix-Based Autologous Chondrocyte Implantation: Results After 3-Year Follow-up

Background: Third-generation autologous chondrocyte implantation (ACI) is an established method for treatment of full-thickness cartilage defects in the knee joint. Subchondral bone marrow edema (BME) is frequently observed after ACI, with unknown pathogenesis and clinical relevance. Purpose: To investigate the occurrence and clinical relevance of BME after third-generation ACI in the knee joint during the postoperative course of 36 months. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 38 circumscribed full-thickness cartilage defects in 30 patients were included in this study. All defects were treated with third-generation ACI (Novocart 3D). A standardized MRI examination was carried out after 1.5, 3, 6, 12, 24, and 36 months. Bone marrow edema was observed in 78.9% of defects over the postoperative course, with initial occurrence in the first 12 months. The size of the BMEs were determined according to their maximum diameter and were classified as small (