What is knee discoid meniscus?

The menisci are crescent-shaped cartilaginous structures located between the femur (thigh bone) and the tibia (shin bone) in the knee. There are two menisci in the knee, the medial (inner) and lateral (outer) meniscus. Their shape helps reduce the incongruity between the articular surfaces of the femur and tibia, increasing the contact surface area of the joint bodies. They contribute to load transmission, decrease pressure on the articular cartilage, and play a role in knee stability and the distribution of synovial fluid within the knee.

A discoid meniscus is a congenital anatomical variation of the knee meniscus. Instead of the normal crescent shape, the meniscus has an altered shape, resembling a ring or disc. The discoid meniscus is thicker and composed of lower-quality tissue. This altered meniscus is typically unstable and less suited to withstand mechanical stress in the knee, making it more prone to tearing. Moreover, it was previously believed that all meniscal injuries in children were associated with a discoid shape. However, an increasing number of children involved in sports present to pediatric orthopedic clinics with tears in a normal-shaped meniscus.

How to diagnose knee discoid meniscus?

Clinical manifestations of a discoid meniscus in children can range from completely asymptomatic to extremely painful. Symptoms include clicking, pain around the joint, buckling, and restricted knee mobility. The snapping knee syndrome, involving clicking with mobility blockages, is often considered a characteristic sign of a discoid meniscus in children up to ten years of age. To diagnose a discoid meniscus in children, magnetic resonance imaging (MRI) is typically used because menisci are not visible on X-ray images. MRI provides a detailed view of the structures inside the knee, including the shape and condition of the meniscus.

How to treat knee discoid meniscus?

The treatment of a discoid meniscus in children depends on the symptoms and issues it causes. If the discoid meniscus is not causing problems, avoiding activities that increase the risk of injury may be recommended. However, if it causes mechanical issues, pain, or swelling after a tear, surgical intervention is often recommended. Knee arthroscopy is commonly used as a treatment method, where the discoid meniscus is shaped to closely resemble a normal meniscus. In some cases, if the discoid meniscus is causing instability, it may be sutured to the joint capsule during the surgical procedure. After surgery, physical therapy follows to regain full range of motion and muscle strength, with a gradual return to normal activities and sports within about six months.

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