→ a rupture of the cushioning cartilage within the knee joint.

What is a meniscus?

The meniscus is a firm pad of cartilage between the femur (thigh bone) and tibia (shinbone) (cartilage is a tough, flexible tissue that covers bone endings and allows them to slide against each other painlessly). The meniscus is actually comprised of two parts, or menisci. The inner (medial) meniscus is shaped in a crescent-like ‘C’ (hence the word ‘meniscus’, which is derived from the Greek word for moon). The outer (lateral) meniscus has a tighter, ‘U’ shape. Together, the two parts work somewhat like the shock absorber of a car, bearing and spreading weight across the joint and helping to stabilize and protect the adjacent bones.

How does a meniscal tear occur?

Meniscal tears are one of the most common forms of cartilage injury. Doctors usually classify them in two ways, as traumatic or degenerative. In a traumatic injury, a sudden, forceful impact to the front or side of the knee may cause either menisci to tear as the knee joint jolts out of position. Tears can also happen when the knee twists suddenly, for instance when the leg ‘plants’ on the ground and causes the joint to over-rotate. These injuries are most common during sporting activity – in a football or rugby tackle, for example, or in a sport that involves frequent twists and pivots, such as tennis or basketball. By contrast, degenerative tears happen through gradual deterioration of the meniscus. Since the elasticity of our cartilage declines with age, tears can happen more easily as we get older. Meniscal tears can also be complicated by broken cartilage; pieces of cartilage can sometimes break off and become lodged in the knee joint, causing the knee to lock up.

How is a meniscal tear diagnosed?

Diagnosing a meniscal tear starts with an examination of your knee and an analysis of your symptoms. Pain from a tear to the menisci can be felt along the joint, or more generally across the whole of the knee; it often gets worse during activities like squatting and twisting. Meniscal tears can also be accompanied by swelling, stiffness and difficulty in bending and straightening the knee, a clicking or grinding sensation in the joint, and sometimes by a ‘popping’ sensation at the time of the injury. You may also be asked to have an x-ray or MRI scan to help diagnose the injury.

What happens next?

The first line of treatment for a meniscal tear is rest, accompanied by elevation of the knee and regular application of an ice pack to reduce swelling; ordinary painkillers and physical supports, such as a knee brace, may also be helpful. Minor meniscal tears may heal naturally within a few weeks. Traumatic tears are less likely to heal independently and may eventually require surgery. Surgery tends to focus on repairing or replacing the torn cartilage, or on removing the loose cartilage that has caught in the joint. In the most severe cases it may lead to a knee joint replacement.