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.

Cartilage lesions that are present at surgery progress to cartilage degeneration in the early phase after ACLR.

Case series; Level of evidence, 4.

T1 is the spin-lattice relaxation in the rotating frame magnetic resonance imaging. Sagittal T1 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 T1 value (milliseconds) of each ROI were recorded, and differences between patients with and without cartilage lesions were evaluated. The relationship between changes in the T1 value and meniscal tears was also studied.

Arthroscopy at ACLR detected cartilage lesions in 15 MFCs, 7 LFCs, and 2 LTPs. The baseline T1 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 T1 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 T1 value of the MFC increased during the year after treatment (P = .002). There was no significant difference in the baseline and follow-up T1 value in patients with or without meniscal tears on each side although the T1 value of the MFC, MTP, and LFC increased during the first year after surgery regardless of the presence or absence of meniscal injuries.

Using T1 mapping to detect minimal changes, our study demonstrated that cartilage lesions are related to progressive degenerative cartilage changes during the early phase after ACLR.