The discoid lateral meniscus in children: a narrative review of pathology, diagnosis and treatment

Abstract

Background and objective: The discoid lateral meniscus (DLM) is a congenital abnormality of the meniscal shape, characterized by a typical central hypertrophy and a diameter larger than a regular meniscus, potentially leading to knee pain and symptoms, especially in children. The present study provides an update and a general review of this uncommon meniscal pathology. The incidence of discoid meniscus is about 0.4-17% for the lateral and 0.1-0.3% for the medial, although, being often asymptomatic, the true prevalence is unknown. We aim to enhance awareness on this subject to medical care provider.

Methods: A literature search was performed on PubMed, including articles written in English until October 2021.

Key content and findings: The articles regarding etiology, diagnosis and management of DLM in children or in patients younger than 18 years were reviewed using the narrative approach.

Conclusions: Recent literature has shown that DLM is one of the most frequent congenital anomalies of the knee encountered during childhood. While asymptomatic children with incidental finding can be managed nonoperatively, symptomatic painful DLM should be addressed surgically, restoring typical anatomy using saucerization, tear repair, and stable fixation of the meniscus. The risk of osteoarthritis progression seems to be higher in children with operated DLM, imposing prolonged follow-up and cartilage preserving strategies for these patients.

Keywords: Knee; children; discoid lateral meniscus (DLM); meniscus; saucerization.

Figure 1

Meniscal tissue and cell morphology observed by transmission electron microscopy. (A,B,F) Meniscal sample collected from multi-organ donor. (C,D,E) Sample from discoid meniscus knee of a 12-year-old girl.

Figure 2

Extracellular matrix composition assessed by histological analysis (safranin O-fast green staining; magnification, ×10). (A) Sample from discoid meniscus knee of a 12-year-old girl. (B) Meniscal sample collected from multi-organ donor.

Figure 3

Left knee MRI of two 9-year-old girls (courtesy of Giovanni Trisolino). (A) Patient with a normal meniscus. (B) Patient with discoid lateral meniscus. MRI, magnetic resonance imaging.

Figure 4

Arthroscopic image of the knee of a 12-year-old girl, with a symptomatic discoid meniscus (courtesy of Giovanni Trisolino). A complete lateral discoid meniscus (A), that underwent arthroscopic saucerization (B).

Figure 5

A case of a male 15-year-old soccer player who sustained a DLM traumatic lesion (courtesy of Alberto Grassi). (A,B) Preoperative MRI showing DLM with traumatic lesion and detachment from its posterolateral capsular attachments (yellow arrow) (A) and dislocation toward the intercondylar notch (red arrow) (B). (C,D) Post-operative MRI at 4-months follow-up that show normal meniscal shape with anatomic position of posterior horn (yellow arrow) (C) and capsular healing of the peripheral rim (red arrow) (D). Three years after the repair, the patient was performing soccer without symptoms. DLM, discoid lateral meniscus; MRI, magnetic resonance imaging.

Figure 6

A case of a male 15-year-old soccer player who sustained a DLM traumatic lesion (courtesy of Alberto Grassi). (A) Arthroscopically, it is possible to see the capsular detachment with a thin peripheral rim. (B) The central portion of the DLM is hypertrophic and is saucerized to re-shape the meniscus. (C) Multiple all-inside and out-in sutures are placed to repair the peripheral tear and stabilize the meniscus. (D) Final aspect after saucerization and repair, with a shape that resemble a normal meniscus. DLM, discoid lateral meniscus.

Figure 7

Lateral osteoarthritis in a 20-year-old female (courtesy of Stefano Zaffagnini). Three years after lateral meniscectomy of a discoid lateral meniscus performed in another hospital, and candidate for Meniscal Allograft Transplantation.