Tissue distribution and measurement of cartilage oligomeric matrix proteinin patients with magnetic resonance imaging-detected bone bruises after acute anterior cruciate ligament tears

Histologic and immunostaining analyses were performed on articular cartilag e/subchondral bone biopsy specimens overlying MRI-detected bone bruises in 12 patients with anterior cruciate ligament (ACL) tears. Staining with tolu idine blue for proteoglycan revealed loss of staining from the superficial portion of the articular cartilage. Immunostaining for cartilage oligomeric matrix protein (COMP) showed an increased staining in the superficial matr ix of the articular cartilage. Using polyclonal antisera against COMP, the authors performed a competitive enzyme-linked immunosorbent assay (ELISA) o n the synovial fluid from the injured and uninjured knees. There was an app roximately 10-fold higher synovial fluid COMP levels in injured knees. The COMP levels were greater in those patients who had synovial fluid samples h arvested closer to the date of initial injury. Western blot analysis of the synovial fluid showed an increased presence of COMP degradation fragments from injured knees. These results are indicative of a significant injury to the articular cartilage, and may represent preclinical posttraumatic osteo arthritic lesions. (C) 2001 Orthopaedic Research Society. Published by Else vier Science Ltd. All rights reserved.