Direct MR arthrography of plica synovialis mediopatellaris

Objective: To evaluate the efficacy of direct MR arthrography for diagnosing plica synovialis mediopatellaris (PSM).Material and Methods: Twenty-two knees of 19 patients were examined by direct MR arthrography. In 19 of those knees, field-echo T2*-weighted transaxial images were obtained with intra-articular administration of 40 ml of saline ("direct MR arthrography"). In the other 3 knees, T1-weighted transaxial images were obtained with intra-articular administration of 40 ml of gadopentetate dimeglumine. Conventional MR images were evaluated prior to direct MR arthrography in 12 of the 22 knees. The results of direct MR arthrography and conventional MR imaging were compared with the arthroscopic findings.Results: Direct MR arthrography demonstrated 17 of 19 PSMs proved on arthroscopy. The features of 16 PSMs on direct MR arthrography corresponded accurately with the arthroscopic classification. Conventional MR demonstrated only 3 plicae.Conclusion: Direct MR arthrography enabled accurate diagnosis of PSMs and could replace diagnostic arthroscopy.