Early Cartilage Changes After Anterior Cruciate Ligament Injury: Evaluation With Imaging and Serum Biomarkers-A Pilot Study.

PURPOSE: To determine if magnetic resonance imaging markers of cartilage matrix and morphology and circulating serum biomarkers of inflammation and matrix degradation differ over time in patients with anterior cruciate ligament (ACL) injury and bone marrow edema lesions (BMELs) when compared with matched control subjects.

METHODS: We performed a case-control study, in which 11 ACL-injured subjects scheduled to undergo reconstruction and 11 matched control subjects were scheduled for testing. Participants were selected for the ACL reconstruction (ACLR) group if they injured their ACL while participating in sports, were aged 14 to 30 years, had 1 or more BMELs, and were scheduled to undergo bone-patellar tendon-bone ACLR. Testing required patients to undergo magnetic resonance imaging for measurement of T2 relaxation times in standardized regions of interest over the medial and lateral tibial plateaus and femoral condyles and have blood drawn for measurement of cartilage oligomeric matrix protein (COMP) and C-reactive protein levels before ligament reconstruction and 1 year after surgery.

RESULTS: ACL patients had prolonged T2 relaxation times, indicative of cartilage matrix degradation, in the superficial central lateral tibial plateau (P = .02) and deep medial tibial plateau when compared with control subjects (P = .0001). Prolonged T2 relaxation times were also noted over the lateral femoral condyle at baseline for ACL patients compared with control subjects (P = .001), but the differences resolved by 1 year (P = .98). Circulating serum COMP levels were greater in ACL patients (233.23 ± 88.26 ng/mL) compared with control subjects (169.05 ± 64.53 ng/mL, P = .05).

CONCLUSIONS: T2 mapping showed prolonged relaxation times in the lateral compartment of the knee in ACLR patients with lateral BMELs. Furthermore, prolonged T2 relaxation times were apparent in the medial compartment of the knee in ACL-injured patients where bone marrow lesions were not present. Higher serum COMP levels were present in ACL-injured subjects when compared with control subjects.

LEVEL OF EVIDENCE: Level II, prospective case-control study.