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Background: Articular cartilage degeneration can develop after anterior cruciate ligament reconstruction (ACLR). Although radiological studies have identified risk factors for the progression of degenerative cartilage changes in the long term, risk factors in the early postoperative period remain to be documented., Hypothesis: Cartilage lesions that are present at surgery progress to cartilage degeneration in the early phase after ACLR., Study Design: Case series; Level of evidence, 4., Methods: T1ρ is the spin-lattice relaxation in the rotating frame magnetic resonance imaging. Sagittal T1ρ maps of the femorotibial joint were obtained before and 1 year after ACLR in 23 patients with ACL injuries. Four regions of interest (ROIs) were placed on images of the cartilage in the medial and lateral femoral condyle (MFC, LFC) and the medial and lateral tibia plateau (MTP, LTP). Changes in the T1ρ value (milliseconds) of each ROI were recorded, and differences between patients with and without cartilage lesions were evaluated. The relationship between changes in the T1ρ value and meniscal tears was also studied., Results: Arthroscopy at ACLR detected cartilage lesions in 15 MFCs, 7 LFCs, and 2 LTPs. The baseline T1ρ value of the MFC and LFC was significantly higher in patients with cartilage lesions (MFC, 40.7 ms; LFC, 42.2 ms) than in patients without cartilage lesions (MFC, 38.0 ms, P = .025; LFC, 39.4 ms, P = .010). At 1-year follow-up, the T1ρ value of the MFC and LFC was also significantly higher in patients with lesions (MFC, 43.1 ms; LFC, 42.7 ms) than in patients without such lesions (MFC, 39.1 ms, P = .002; LFC, 40.4 ms, P = .023, respectively). In patients with cartilage injury, the T1ρ value of the MFC increased during the year after treatment (P = .002). There was no significant difference in the baseline and follow-up T1ρ value in patients with or without meniscal tears on each side although the T1ρ value of the MFC, MTP, and LFC increased during the first year after surgery regardless of the presence or absence of meniscal injuries., Conclusion: Using T1ρ mapping to detect minimal changes, our study demonstrated that cartilage lesions are related to progressive degenerative cartilage changes during the early phase after ACLR.

Objective: To study the effects of aging and cartilage degeneration of the proximal tibiofibular- and femorotibial joint (PTFJ, FTJ) on the cartilage of the PTFJ using T(1)ρ and T(2) mapping., Materials and Methods: We performed sagittal T(1)ρ and T(2) mapping of the PTFJ and FTJ on 55 subjects with knee disorders. We placed 3 regions of interest (ROIs) on images of the cartilage in the PTFJ, medial femoral condyle (MFC), and medial tibia plateau (MTP). Correlation analysis was performed for the T(1)ρ and T(2) values of each ROI and the patient age and the osteoarthritic grade of the PTFJ and FTJ., Results: The T(1)ρ and T(2) values of the PTFJ were affected neither by aging nor the osteoarthritic grade of the FTJ. Values of the FTJ normalized to PTFJ values were correlated with the osteoarthritic grade of the FTJ in the MFC (r=0.851 and 0.779, respectively) and the MTP (r=0.635 and 0.762, respectively). There was a significant difference in the T(1)ρ but not the T(2) value of the PTFJ and MFC between normal and mildly osteoarthritic cartilage of each joint., Conclusion: We document that the T(1)ρ and T(2) values of PTFJ cartilage were not affected by aging or cartilage degeneration in the FTJ. The T(1)ρ value of the PTFJ may represent a useful internal standard reference for evaluating early degeneration of the FTJ., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Purpose: To determine the relationship between changes in the extracellular matrix (ECM) and T(1ρ) and T(2) values in vivo. The ECM is composed of proteoglycan (PG), collagen, and water. It has been unclear which of the ECM constituents affects T(1ρ) and T(2) mapping in living human cartilage., Materials and Methods: Sagittal T(1ρ) and T(2) maps were preoperatively obtained from 20 knee osteoarthritis patients. Osteochondral samples harvested from the resected tibial plateaus during total knee arthroplasty were consistent with the MRIs of the patients' knees. Parameters that included histological grading of cartilage degeneration, glycosaminoglycan (GAG) content (which constitutes PG), presence of collagen anisotropy and water content were evaluated along with T(1ρ) and T(2) values, and statistical analysis was performed using multiple regression analysis., Results: T(1ρ) and T(2) values were significantly correlated with the degree of cartilage degeneration (β = 0.397 and 0.357, respectively) and the GAG content (β = -0.340 and -0.244, respectively)., Conclusion: The present study demonstrated that T(1ρ) and T(2) values reflect the GAG content of the cartilage and can indicate cartilage degeneration in vivo. Use of these parameters can facilitate the noninvasive diagnosis and evaluation of cartilage degeneration., (Copyright © 2011 Wiley Periodicals, Inc.)