Bilateral discoid lateral meniscus in knees: evaluation of the contralateral knee in patients with symptomatic discoid lateral meniscus.

PURPOSE

The aim of this study was to analyze, by use of magnetic resonance imaging (MRI), the contralateral discoid lateral meniscus (DLM) status of 33 patients who underwent an operation for a symptomatic DLM.

METHODS

This diagnostic study included 33 consecutive patients who underwent arthroscopic surgery for a unilaterally symptomatic DLM. All patients' contralateral knees were checked with simple radiographs and MRI scans. Knees were also evaluated through physical examinations and a clinical scoring system. On the basis of the MRI findings, DLM was categorized into 3 types: normal type, incomplete discoid type, and complete discoid type. The tear patterns of the lateral menisci as imaged by radiographs and the associated chondral lesions imaged by MRI were analyzed by consensus in the bilateral knees.

RESULTS

All but 1 of the contralateral, asymptomatic knees (97%) were diagnosed by MRI to have complete or incomplete DLM. DLMs with tears were found in the contralateral knees in 11 cases (33%), and chondral lesions were found in 4 (12%) of the complete discoid type cases. On radiography, 23 (70%) of the 33 contralateral knees showed characteristic findings of DLM. We found that 29 pairs of knees (88%) had the same lateral meniscus shape on MRI. A κ analysis showed significant and good agreement between the radiographic findings, the tear pattern of the lateral menisci, and the associated chondral lesions on MRI scans in bilateral knees.

CONCLUSIONS

DLM commonly occurs bilaterally in patients with symptomatic, unilateral surgical DLM, although this finding was applicable only to young, Asian male patients. Characteristic radiographic findings and the MRI findings of symptomatic DLM patients were significantly correlated between both knees.

LEVEL OF EVIDENCE

Level I, testing of previously developed diagnostic criteria in a series of consecutive patients with universally applied reference gold standard.