Association between injury-related factors and cartilage T2 relaxation time in the subacute phase in patients after anterior cruciate ligament injury.

OBJECTIVE To investigate associations between meniscal tear, bone marrow lesions (BMLs), and post-injury knee loading, with cartilage T2 relaxation times on knee magnetic resonance imaging (MRI) in the subacute phase following acute anterior cruciate ligament (ACL) injury. DESIGN We studied both knees of 128 patients with ACL injury. The presence of meniscal tears and BMLs were determined on subacute MRI (mean 29 days [SD 13] post injury), and post-injury knee loading was measured using an accelerometer. Manual cartilage segmentation and T2 relaxation time mapping of tibiofemoral cartilage was performed on both knees. We used multiple linear regression models adjusted for age, sex, body mass index, and time from injury to MRI to evaluate the association between exposures and cartilage T2 relaxation times in the ACL injured knee between individuals. We also performed paired t-tests for comparisons with the individual's non-ACL injured contralateral knee free of the exposure of interest. RESULTS There was an association between ipsilateral meniscal tear and prolonged T2 relaxation time in the superficial cartilage of posterior tibia in both compartments (beta-coefficient medial: 2.88, [95% CI 1.16-4.61], beta-coefficient lateral: 1.88, [0.17-3.58]). Findings were confirmed in the paired analyses with contralateral knees (mean T2 difference 1.43, [0.33-2.53] and 2.10 [0.48-3.71] respectively). We found no essential associations for the other cartilage subregions or for BMLs and knee loading. CONCLUSION In the subacute phase after ACL injury, ipsilateral meniscal tear is associated with prolonged cartilage T2 relaxation time in the posterior tibia. This finding highlights the importance of meniscus function in the ACL-injured knee.