MRI images of chondromalacia patella show patellar articular surface changes, patellar cartilage signal changes, and malalignment of the patellofemoral joint. The diagnostic value of MRI for chondromalacia patella is high, which can clearly show the extent and degree of abnormal lesion signals in the underlying, middle and superficial cartilage. 1. Patellar articular surface changes: chondromalacia patella can be seen on MRI in different degrees of patellar chondromalacia with interruption of the patellar cartilage surface, defects and subchondral bone marrow edema. 2. Patellar cartilage signal changes: in MRI staging of chondromalacia patella, stage I shows normal articular cartilage contour and signal intensity changes; stage II shows localized swelling within the cartilage and signal abnormality in T1-weighted image (T1WI) and T2-weighted image (T2WI). Stage III: irregular cartilage and localized thinning; Stage IV: loss of articular cartilage and subchondral osteosclerosis and capsulitis. 3. Patellofemoral joint malalignment: Chondromalacia patella will cause joint surface degeneration and bone redundancy in the late stage, resulting in patellofemoral joint malalignment and patella subluxation, which is a typical imaging manifestation of chondromalacia patella.