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Published on: January 23, 2018
Discoid medial meniscus
Yomei Tachibana1, Yuji Yamazaki, Setsuo Ninomiya
1Division of Sports Medicine, Saitama Medical School, Iruma-gun, Saitama, Japan. yomei@saitama-med.ac.jp
Abstract:
A discoid medial meniscus is an extremely rare anomaly. We present 4 cases of symptomatic discoid medial meniscus. Furthermore, magnetic resonance imaging (MRI) of the unaffected knee was obtained in 3 cases, and 1 patient had bilateral discoid medial menisci as well as a unilateral discoid lateral meniscus proven by MRI. Another patient had bilateral discoid medial menisci. In one of the other 2 cases, an MRI of the unaffected knee was not obtained. However, in the involved knees of both cases, medial and lateral menisci were discoid. The incidence of bilateral discoid medial menisci is unknown. In the past, the diagnosis of a discoid meniscus was made with an arthrogram or at arthrotomy. Therefore, whether some of the unilateral cases reported in the literature might have been bilateral is unknown. The reported prevalence of bilateral discoid medial menisci will probably increase, because when a discoid medial meniscus is encountered currently, an MRI is used to find knee disorders, including in the contralateral knee. Axial multiplanar gradient-recalled-echo imaging could provide images of the discoid meniscus, depicted in its entirety in one section. This would make the recognition of a discoid meniscus simple.
Insights
Discoid medial meniscus is a rare anomaly. This study highlights 4 cases and suggests bilateral cases may be more common than previously thought, especially with advanced MRI diagnostics.
Area of Science:
- Orthopedics
- Radiology
- Medical Imaging
Background:
- A discoid meniscus is a rare congenital anomaly where the meniscus has a disc-like shape instead of the usual crescent shape.
- Symptomatic discoid medial menisci are exceptionally rare, presenting diagnostic challenges.
Observation:
- This study presents four cases of symptomatic discoid medial meniscus.
- Magnetic resonance imaging (MRI) revealed bilateral discoid medial menisci in two patients and unilateral discoid lateral meniscus in one.
- In two cases, both medial and lateral menisci were discoid in the affected knees.
Findings:
- The actual incidence of bilateral discoid medial menisci remains unknown.
- Previous diagnostic methods like arthrograms or arthrotomy may have underestimated the prevalence of bilateral cases.
- Modern MRI techniques, particularly axial multiplanar gradient-recalled-echo imaging, simplify the recognition of discoid menisci.
Implications:
- The prevalence of bilateral discoid medial menisci is likely underestimated and may increase with routine contralateral knee MRI screening.
- Improved MRI visualization can aid in accurate diagnosis and understanding of meniscal anomalies.
- This finding has implications for surgical planning and understanding knee biomechanics in patients with meniscal variations.
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