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Case Reports
. 2025 Apr 4;17(4):e81729.
doi: 10.7759/cureus.81729. eCollection 2025 Apr.

A Ring-Shaped Lateral Meniscus in an Anterior Cruciate Ligament Reconstruction Surgery

Mohd Fairudz Mohd Miswan  1   2 , Sharifah Nor Amirah Alsagoff  1   2 , Mohd Yusoff Yahaya  1   2 , Mohamed Faizal Sikkandar  1   2 , Mohd Shukry Mohd Khalid  3   4
Affiliations
Case Reports

A Ring-Shaped Lateral Meniscus in an Anterior Cruciate Ligament Reconstruction Surgery

Mohd Fairudz Mohd Miswan et al. Cureus. .

Abstract

The ring-shaped meniscus is a rare variant of meniscus anomalies. We report a case of a young man who experienced right knee instability following a sports-related injury. Clinical examination suggested an anterior cruciate ligament (ACL) tear, which was confirmed through imaging studies. Intra-operatively, an incidental finding revealed the presence of a ring-shaped lateral meniscus. We discuss the diagnostic features of this uncommon abnormality.

Keywords: acl reconstruction; anatomical variant; discoid meniscus; lateral meniscus; ring-shaped meniscus.

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Conflict of interest statement

Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. MR images showing the aberrant meniscal tissue (red arrow).
(a) Coronal view demonstrating the inner portion of the ring-shaped meniscus, known as the "mirror image sign", a triangular structure mirroring the body of the meniscus. (b) Sagittal view showing "central bow tie sign" signifying a lateral meniscus fragment in the notch. (c) Axial view demonstrating a central portion or the intermeniscal bridge of the lateral meniscus fragment. MR: magnetic resonance
Figure 2
Figure 2. Arthroscopic findings of the lateral ring-shaped meniscus of the right knee
(a) Intermeniscal bridge (red star) in between the anterior and posterior horns of the lateral meniscus and stable on probing. Blue arrowheads demarcating the inner edge of the intermeniscal bridge. (b) Anterior, lateral, and posterior aspects of the ring meniscus with no evidence of tears. AH: anterior horn; PH: posterior horn; LFC: lateral femoral condyle
Figure 3
Figure 3. Arthroscopic image of the relation of the intermeniscal bridge to surrounding structures
(a) Intermeniscal tissue firmly attached on the lateral tibial spine lateral to the ACL stump. (b) Relation between the inner portion of the RSM and the reconstructed ACL. ACL: anterior cruciate ligament; ACLr: reconstructed ACL; RSM: ring-shaped meniscus; LFC: lateral femoral condyle; red star: intermeniscal bridge of the lateral RSM
See this image and copyright information in PMC

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