ARE MR-IMAGING SIGNS OF MENISCOCAPSULAR SEPARATION VALID

PURPOSE: To define the positive predictive value (PPV) for the magneti c resonance (MR) imaging diagnosis of meniscocapsular separation in th e knee. MATERIALS AND METHODS: The MR reports of 52 patients aged 16-7 5 years who had a prospective MR diagnosis of meniscocapsular injury w ere correlated with arthroscopic results. MR images obtained in 50 of these patients were retrospectively reviewed for specific signs of men iscocapsular separation, which included meniscal displacement peripher al meniscal corner tears, increased perimeniscal signal intensity, flu id deep to the medial collateral ligament, and abnormal lateral fascic les. MR findings were correlated with arthroscopic findings. RESULTS: For the prospective MR interpretations, the PPV for meniscocapsular se paration was 9% medially and 13% laterally. Meniscal displacement (mea sured from the meniscal edge to the tibia) was as great as 10 mm media lly or 13 mm laterally without meniscocapsular tears at arthroscopy. M eniscal displacement did not correlate with effusion. Meniscal corner tears had a PPV of 0% medially and 50% laterally. Fluid at the menisco capsular border and fluid deep to the medial collateral ligament were poor predictors of meniscocapsular abnormalities. Abnormal-appearing m eniscal fascicles had a PPV of 8% for lateral meniscocapsular-separati on. CONCLUSION: The PPV for the MR diagnosis of meniscocapsular separa tion is low; the reported MR signs correlate poorly with arthroscopic findings.