Objective To analyze the auxiliary role of MRI T2 mapping imaging in the clinical diagnosis of knee cartilage injury. Methods: 117 patients with knee cartilage injury admitted to our hospital from November 2023 to November 2024 were selected and included in the injury group. Meanwhile, 69 healthy volunteers who underwent physical examinations in our hospital were selected and included in the control group. All the research subjects underwent MRI T2 mapping imaging, and the T2 values of cartilage in each area of the knee joint in the two groups were detected and compared. Taking arthroscopic results as the gold standard, the detection rate and consistency of T2 mapping imaging combined with conventional sequence examination in diagnosing knee cartilage injury were analyzed. Results The T2 values of the medial and lateral condyles of the femur, the medial and lateral platforms of the tibia, and the patellar cartilage in the injury group were significantly higher than those in the control group (P < 0.05). Meanwhile, the T2 values of the weight-bearing areas of the medial and lateral condyles of the femur in the injury group and the weight-bearing area of the lateral condyle of the femur in the control group were significantly higher than those of their respective non-weight-bearing areas (P < 0.05). The T2 values of the medial non-weight-bearing area of the superficial cartilage of the femur, the weight-bearing and non-weight-bearing areas of the lateral condyle, the inner and outer platforms of the tibia and patellar cartilage in patients with knee cartilage injury were significantly greater than those of each area of the deep cartilage (P < 0.05). Arthroscopic examination of 117 cases showed that there were 187 injured knee joints, including 109 in the right knee and 78 in the left knee. The detection rate by conventional MRI sequence examination was 83.96%, significantly lower than 94.65% of T2 mapping combined with conventional sequence. The consistency of T2 mapping combined with the results of conventional sequence examination and arthroscopic examination was good, and the kappa value was 0.952 (P < 0.05). Conclusion: MRI T2 mapping imaging can measure the changes in cartilage T2 values, and by combining with conventional sequence examinations, the diagnostic value for knee joint cartilage injuries can be improved.