Medial plica syndrome of the knee: diagnosis with dynamic sonography.

PURPOSE To perform a feasibility study of dynamic sonography for the diagnosis of medial plica syndrome of the knee. MATERIALS AND METHODS The study design was approved by the university bioethics board, and all the participants gave informed consent. Inclusion criteria were a palpable medial band, history of painful aching, and giving way or locking, which limited the subject's activity for at least 6 months. Exclusion criteria were a history of trauma with hemarthrosis, previous knee surgery, and arthrosis detectable on radiographs. A prospective evaluation in 88 subjects (56 female subjects, 32 male subjects; mean age, 20 years; range, 7-47 years) who were suspected of having a medial plica and 91 knees was performed. Three sonographic criteria were assessed during patellar movement by using a 12-MHz 38-mm linear transducer: (a) continuous echo sliding over the medial femoral condyle during medial and lateral movement of the patella, (b) entry of the echo under the patella during medial movement of the patella, and (c) pain or discomfort during dynamic sonography. Arthroscopy was the reference standard. An asymptomatic control group consisting of 32 volunteers (mean age, 28 years; range, 10-52 years) and 60 knees was also assessed. RESULTS Arthroscopy revealed 68 plicae with pathologic findings, 61 of which met all three sonographic criteria. Medial plicae with pathologic findings were absent in 23 knees; 19 plicae were correctly diagnosed by using sonography. Diagnostic accuracy was 88%, sensitivity was 90%, and specificity was 83%. In the asymptomatic control group, there were 37 knees without a plica echo, 16 knees with a plica echo that met one criterion, and seven knees that met two criteria. CONCLUSION Dynamic sonography allows detection of abnormalities of medial plicae in the knee, with good sensitivity and specificity.