All MRI scans were obtained with a 3.0-T MRI scanner (Magnetom Trio with TIM system, Siemens Healthcare). Five routine MRI sequences with a section thickness of 4 mm were obtained in all patients. Preoperative and postoperative evaluations of the articular cartilage of the transplanted compartment were performed with the Yulish score41 (grade 0 = normal; grade 1 = normal contour 6 abnormal signal; grade 2 = superficial fraying, erosion, or ulceration of <50%; grade 3 = partial-thickness defect of >50% but <100%; grade 4 = full-thickness cartilage loss). The signal of the meniscus allograft in the coronal plane of the T2-weighted fast spin echo sequence was graded on a scale of 0 to 3.

All MRI scans were obtained with a 3.0-T MRI scanner (Magnetom Trio with TIM system, Siemens Healthcare). Five routine MRI sequences with a section thickness of 4 mm were obtained in all patients. Preoperative and postoperative evaluations of the articular cartilage of the transplanted compartment were performed with the Yulish score41 (grade 0 = normal; grade 1 = normal contour 6 abnormal signal; grade 2 = superficial fraying, erosion, or ulceration of <50%; grade 3 = partial-thickness defect of >50% but <100%; grade 4 = full-thickness cartilage loss). The signal of the meniscus allograft in the coronal plane of the T2-weighted fast spin echo sequence was graded on a scale of 0 to 3.

All patients also obtained 45° flexion weightbearing AP radiographs of both the ipsilateral and contralateral sides at final follow-up. The radiograph of the total length of the lower limbs was used to evaluate alignment. In the AP plain radiographs, the shortest distance between the femoral condyle and tibial plateau of the transplanted side was measured and designated as the joint space height. The difference between the ipsilateral and contralateral sides was calculated to identify joint space narrowing. In addition, Kellgren-Lawrence (K-L) grading was used to assess the osteoarthritic status of the knee.