Associations between cartilage proteoglycan density and patient outcomes 12 months following anterior cruciate ligament reconstruction

Background: Lower proteoglycan density (PGD) of the articular cartilage may be an early marker of osteoarthritis following anterior cruciate ligament (ACL) reconstruction (ACL-R). The purpose this study was to determine associations between the Knee Injury and Osteoarthritis Outcomes Score (KOOS) and PGD of the articular cartilage in the femur and tibia 12-months following ACL-R. Methods: We evaluated KOOS pain, symptoms, function in activities of daily living (ADL), function in sport and recreation (Sport), and quality of life (QOL), as well as PGD using T1rho magnetic resonance imaging in 18 individuals 12.50 ± 0.70 months (these are all mean ± standard deviation) following unilateral ACL-R (10 females, eight males; 22.39 ± 4.19 years; Marx Score = 10.93 ± 3.33). Medial and lateral load-bearing portions of the femoral and tibial condyles were sectioned into three (anterior, central and posterior) regions of interest (ROIs). T1rho relaxation times in the ACL-R knee were normalized to the same regions of interest in the non-surgical knees. Alpha levels were set at P ≤ 0.05. Results: Worse KOOS outcomes were significantly associated with greater T1rho relaxation time ratios in the posterior-lateral femoral condyle [pain (r = − 0.54), ADL (r = − 0.56), Sport (r = − 0.62) and QOL (r = − 0.59)] central-lateral femoral condyle [Sport (r = − 0.48) and QOL (r = − 0.42)], and the anterior-medial femoral condyle [Sport (r = − 0.46) and QOL (r = − 0.40)]. There were no significant associations between the KOOS and T1rho outcomes for tibial ROI. Conclusions: Lower PGD of the femoral cartilage in the ACL-R knees was associated with worse patient-reported outcomes.