Diagnostic value of MRI in medial patellar plica: limited classification but link to cartilage injury

To assess the diagnostic value of MRI in classifying medial patellar plica and to examine the relationship between plica classification and the extent of medial femoral condyle cartilage injury as seen on MRI. A retrospective analysis was conducted on MRI data from 156 knees, all of which underwent arthroscopy. The sensitivity, specificity, and accuracy of MRI in diagnosing medial patellar plica were calculated, and the consistency between MRI and arthroscopic findings was assessed. The correlation between MRI-based plica classification and the degree of cartilage injury observed arthroscopically in the medial femoral condyle was also analyzed. Among the 156 knees from 134 patients, the sensitivity, specificity, and accuracy of MRI for diagnosing plica were 87.%, 61%, and 82%, respectively. There was poor agreement between MRI and arthroscopy for plica classification (p < 0.05, Kappa = 0.269). A weak correlation was observed between MRI findings and the degree of cartilage injury in the medial femoral condyle (p < 0.05, r = 0.179). The rates of cartilage injury among MRI-based type A, B, C, and D plica were 42.3%, 18.2%, 52.4%, and 69.2%, respectively. MRI reliably detects medial patellar plica but has limited accuracy for subclassification. Type C and D plicas showed a weak trend toward association with medial femoral condyle cartilage injury, suggesting a potential relationship for future prospective studies.