Isolated lateral meniscus tear in young Artistic gymnast athlete

A 15-years-old female elite Artistic gymnast belong to Italian National Team arrived in our Institute because she felt pain in right knee after landing with extended knees in a training session with asymmetric bars. She was examined by an orthopaedic knee specialist who recommended diagnostic investigation with Magnetic Resonance (MRI).

MRI of the right knee was performed using multiplanar T1-weighted (T1W), T2-weighted (T2W), proton density (PD) with and without fat suppression and short tau inversion recovery (STIR) sequences.

T2 axial and sagittal images (figure 1a and 1b) showed focal hyperintense signal in the midbody of lateral meniscus in the right knee; STIR sequence on sagittal plane (figure 1c) confirmed the existence of radial tear in the midbody of lateral meniscus with the typical “cleft sign”. Anterior cruciate ligament fibers (ACL) were intact and not thickened. There were no sign of bone marrow edema as well as no sign of supra-patellar recess joint effusion.

Background

Menisci are fibrocartilaginous structures of the knee whose functions include load transmission, shock absorption, increasing joint congruity, reducing joint contact stresses, and provide joint lubrication and nutrition; they are also a source of proprioceptive information regarding the position, acceleration and deceleration of the knee joint.

Medial meniscus has a C-shape covering 50% of the medial tibial plateau while the lateral meniscus is more circular and covers approximately 70% of the lateral tibial plateau[1].

Blood supply arises from the periphery through the perimeniscal capillary plexus, being fully vascularised at birth, two-thirds peripheral by 9 months and then gradually decreases; the peripheral rim is known as the ‘red–red’ (R-R) zone and the inner one-third as the ‘white–white’ zone[2].

Radial tears of the midbody of lateral meniscus represent a specific subset of meniscal lesions, commonly found isolated in athletes with stable knees, where circumferential meniscal fibres are completely disrupted, knee biomechanics is compromised, and degenerative changes may occur over time [3].

Clinical Perspective

Meniscal injuries are less prevalent in children and adolescents than in adults. The propensity of lateral meniscal tears to occur in isolation in younger athletes is likely due to its anatomic and biomechanical differences compared to the medial meniscus. The lateral meniscus is more mobile, has less staunch capsular attachments and covers a greater surface area of the lateral plateau than the medial meniscus. These characteristics make isolated tears of the lateral meniscus more likely in a traumatic setting in younger patients [4].

Imaging Perspective

MRI is useful in detecting the presence of a meniscal tear even if has a lower sensitivity and specificity for detecting of meniscal injuries in the young population. A child’s meniscus has high meniscal vascularity, causing signs of intrameniscal enhancement on MRI, and can consequently present as a meniscal tear leading to false positive [1].

Outcome

Treatment of meniscal tears in children and adolescents varies from nonoperative management to partial meniscectomy or meniscal repair [5].

Pre-operative arthroscopy in our case confirmed the presence of isolated radial tear of the body of lateral meniscus in “white zone”. Partial selective meniscectomy was done because tear was considered irreparable.

Take Home Message

Isolated lateral meniscal tears are rare but often detected in young athletes with stable knees. MRI is the gold standard examination for accurate diagnosis of meniscal tears though not exempt from false positives.

The experience of musculoskeletal radiologists is the only feature that may help the orthopaedic surgeon to choose an appropriate treatment in acute setting [3].

Written informed patient consent for publication has been obtained.