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Case Reports
. 2024 Nov;14(11):15-19.
doi: 10.13107/jocr.2024.v14.i11.4898.

Flag Sign: A Case Report of an Unusual Magnetic Resonance Imaging Finding of a Medial Meniscal Root Fragment in an Adolescent Water Polo Player

Panagiotis Antzoulas  1 , Theodoros Stavropoulos  1 , Maria Dimitra Kouzeli  2 , Vasileios Giannatos  1 , Vasileios Papathanidis  1 , Antonios Kouzelis  1
Affiliations
Case Reports

Flag Sign: A Case Report of an Unusual Magnetic Resonance Imaging Finding of a Medial Meniscal Root Fragment in an Adolescent Water Polo Player

Panagiotis Antzoulas et al. J Orthop Case Rep. 2024 Nov.

Abstract

Introduction: A meniscus tear ranks among the most common sports-related injuries, especially among athletes. Sudden, twisting movements, such as pivoting to catch a ball, usually in contact sports, and can tear the meniscus. Magnetic resonance imaging (MRI) technology is extensively utilized for identifying meniscal tears. A flag sign on an MRI typically indicates a partial or complete meniscal root tear. We present a case where a "flag sign" was attributed to a medial meniscal root fragment in an adolescent water polo player.

Case report: A 15-year-old male patient suffered a knee injury (mild swelling and pain) while playing as a goalkeeper in water polo. A physical examination revealed negative Lachman and positive medial McMurray tests. MRI images showed a typical flag sign, without any other concomitant injuries. An arthroscopic medial meniscectomy was performed. 8 months post-operatively the injuries were well healed. In this instance, the flag sign caused interference with the MRI evaluation of an anterior cruciate ligament (ACL) injury.

Conclusion: This case highlights the importance for clinicians to meticulously assess both the morphological changes in the meniscus and its relationship with the femoral condyle before arriving at a definitive diagnosis even in the athletes of non-contact sports. The meniscal "flag sign" mimics the ACL signal on MRI.

Keywords: Meniscus; arthroscopy; flag sign; injury; knee; tear.

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Conflict of interest statement

Conflict of Interest: Nil

Figures

Figure 1
Figure 1
Sagittal magnetic resonance image shows the “flag sign,” a meniscal fragment (arrow).
Figure 2
Figure 2
A meniscal fragment (arrow) has been displaced into the intercondylar notch and resembles the anterior cruciate ligament on a coronal magnetic resonance imaging.
Figure 2
Figure 2
Arthroscopy. (a, b, c) A free fragment of the medial meniscus posterior root has moved to the intercondylar eminence and resembles a “flag sign.” (d) Resetting the medial meniscus. (e) The repaired lateral meniscus.
See this image and copyright information in PMC

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