MR imaging findings in patients with a surgically significant mediopatellar plica.

PURPOSE: To identify MR imaging findings seen in patients with an arthroscopically confirmed significant plica. MATERIALS AND METHODS: MR and arthroscopy reports of 450 patients were reviewed. Nine patients were identified with an arthroscopically significant plica that was resected. Nine patients from these 450 were randomly chosen as a control group. Different criteria were evaluated on the MR images of all patients including: interposition of plica, number of slices with interposition, presence of fluid (focal or generalized), and thickening of the plica. RESULTS: Interposition was found on 3 to 10 transverse imaging slices in the study group (mean, 5.9), and 1 to 4 imaging slices in the control group (mean, 3). Thickening was present in 4/9 patients of the study group and 2/9 patients in the control group. Focal fluid, out of proportion to fluid in the remainder of the joint was found in all patients of the study group and in none of the control group. CONCLUSION: Interposition of the plica on more than 5 transverse slices, and focal fluid adjacent to the plica may suggest the presence of a plica that will be considered significant at arthroscopy.