Sensitivity of MRI for articular cartilage lesions of the patellae

Background and Aims: Reliable diagnosis of articular cartilage lesions of the patellae is often based on arthroscopy. However, unnecessary arthroscopies should be avoided. The aim of this study was to assess the sensitivity and applicability of MRI to diagnosing articular cartilage lesions of the patellae. Materials and Methods: We identified 74 consecutive males (mean age 21 years, range 18-28) from the medical records of our institute with the sole diagnosis of articular cartilage lesions of the patellae based on arthroscopy. Magnetic resonance imaging was performed with 1.0 Tesla scanner a mean of 4 weeks before arthroscopy. Sensitivity of symptoms, and MRI for the diagnosis was calculated. Results: Based on arthroscopy, 20 (27%) cases of cartilage lesions of the patellae were grade-I, 32 (43%) were grade-II, and 22 (30%) were grade-II. MRI revealed cartilage lesions of the patellae in 49 knees (66%), indicating that the sensitivity of MRI was 66%(95% CI: 53%-74%). MRI sensitivity increased with the severity of chondral lesions: all grade III to IV lesions were detected (sensitivity 100%, 95% CI: 85%-100%) by MRI. Grade of articular cartilage lesions of the patellae based on arthroscopy was not associated with clinical symptoms (p = 0.61). Conclusions: The sensitivity of 1.0 Tesla MRI for detecting grade-I lesions was low and could not be used to confirm the diagnosis of articular cartilage lesions of the patellae. For the detection of more severe grade-II to II lesions, the MRI sensitivity was markedly higher. MRI may thus be considered an accurate diagnostic tool for identifying more severe cases of articular cartilage lesions of the patellae.