Discoid menisci of the knee: MR imaging appearance

Area of Science:

• Orthopedic Surgery
• Radiology
• Medical Imaging

Background:

• Discoid menisci are a common knee anomaly.
• Existing diagnostic criteria rely on arthrography.
• Magnetic resonance (MR) imaging has recognized enlarged menisci, but lacks specific diagnostic criteria.

Purpose of the Study:

• To establish diagnostic criteria for discoid menisci using MR imaging.
• To evaluate the accuracy of MR imaging in diagnosing discoid menisci and associated tears.

Main Methods:

• Review of MR images from 29 patients with suspected discoid menisci.
• Definition of discoid meniscus: continuity between anterior and posterior horns on ≥3 contiguous 5-mm sagittal images.
• Analysis of high-resolution coronal images for meniscus width.
• Correlation with arthroscopic findings in 10 cases.

Main Results:

• MR imaging criteria identified discoid menisci based on meniscal continuity.
• Coronal views showed significant width differences in about one-third of cases.
• MR imaging correctly diagnosed 6 of 10 discoid menisci.
• MR imaging identified 2 of 3 meniscal tears seen arthroscopically.

Conclusions:

• MR imaging can reliably diagnose discoid menisci using defined criteria.
• Coronal views provide additional information on meniscus morphology.
• MR imaging shows potential for diagnosing discoid menisci and associated pathology, though with some discrepancies compared to arthroscopy.