The menisci are crescent shaped cartilage structures separating the ends of the femur and tibia inside the knee. There are two menisci in each knee – one medially and one laterally.
The menisci have a number of important functions:
There are two main types of meniscal tear – acute (traumatic) tears and degenerative (wear and tear) tears.
Acute tears most commonly occur in younger patients and often present following sporting or work related injuries. Classically the injury occurs whilst the knee is loaded followed by a twisting and flexing motion. Typically a sudden pain develops at the area of the meniscal tear followed by swelling over a few hours.
Degenerative tears tend to occur in an older population. Over time the menisci become less flexible and rather more friable and susceptible to damage from less traumatic injuries. Classically these tears present with a more insidious onset, with symptoms of intermittent pain, swelling and occasional catching.
Some of the symptoms of meniscal tear include:
Some patients, particularly those with degenerative tears, respond well to conservative treatment with a period of rest and anti-inflammatory tablets followed by physiotherapy. If the symptoms from the tear are minor and not intrusive many patients choose to leave things as they are.
In cases where an acute tear has occurred, the knee is locked or where symptoms are more severe and have not responded to conservative management then surgery is often helpful. The vast majority of meniscal surgery is now performed arthroscopically as a day case procedure.
In some cases the tear in the meniscus may be amenable to repair with sutures. This is more likely to be the case in acute tears in younger patients. Following arthroscopic meniscal repair a knee brace is usually worn for six weeks to prevent excessive knee flexion. Impact loading, twisting and sporting activities should be avoided for three months to give the best chance of healing.
Success rates for meniscal repair are in the range of 60% to 90% depending upon the size, location, timing of the repair and concomitant injuries within the knee.
The majority of meniscal tears are not amenable to repair. In this situation the tear and any unstable cartilage is trimmed away. This helps to prevent further extension of the tear, improves catching symptoms and reduces pain caused by the tear irritating the sensitive synovial lining of the knee.