Meniscal “Ramp” Lesions: Surgical Incidence and the Development of Magnetic Resonance Imaging Diagnostic Criteria

PURPOSE: To establish the magnetic resonance imaging (MRI) and operative incidence of ramp lesions in a consecutive group of patients who had undergone anterior cruciate ligament reconstruction (ACLR) and to propose a graded radiologic classification that seeks to define key preoperative features that most strongly correlate with arthroscopically confirmed ramp lesions. METHODS: After retrospective review, all consecutive patients who underwent ACLR with preoperative MRI over a 16-month period were included in the study. Diagnostic arthroscopy with direct visualization of the posteromedial compartment was used to establish the true incidence of ramp lesions. Three radiologists, blinded to the surgical findings, independently analyzed the MRI scans of all patients and classified the signal intensity at the posterior meniscocapsular junction using 4 criteria (type 1, diffuse increased signal equal to adjacent femoral cartilage; type 2, diffuse increased signal greater than cartilage; type 3, diffuse increased signal plus full-height linear fluid-signal cleft; and type 4, full-height fluid-signal meniscocapsular separation). Interobserver reliability, in addition to sensitivity, specificity, and positive and negative predictive values, was calculated. RESULTS: Of the 93 patients included (mean age, 26.7 years), 11 (11.8%) were confirmed to have ramp lesions on arthroscopy. Inter-rater reliability for the MRI diagnosis of the positive ramp lesions was good, at 0.75. Type 3 criteria were the most accurate, producing average sensitivity and specificity values of 85% and 82%, respectively. CONCLUSIONS: Ramp lesions are not infrequently encountered in ACLR and, if not recognized at the time of surgery, may contribute to inferior outcomes. MRI is an effective method of preoperative assessment, and the presence of type 3 changes should be used as criteria for radiologically definitive ramp lesion diagnosis. CLINICAL RELEVANCE: This study highlights the incidence of meniscal ramp lesions encountered in ACLR surgery and the effectiveness of MRI as a preoperative imaging modality.