What is it?
The menisci, sometimes known as the cartilages, are 2 crescent shaped structures found within the knee on either side (medial and lateral) that act as a shock absorber between the ends of the femur and the tibia. They have a wedge shaped cross sectional area and a highly specialised structure to allow them to perform a number of functions to aid knee joint movement and preserve the articular cartilage.
The functions of the menisci are numerous but include acting as shock absorbers and sharing force transmission from the femur to the tibia with the articular surfaces, working as secondary stabilisers and performing a role to aid lubrication of the knee joint.
It has become evident over recent years that loss of significant amounts of meniscal tissue can cause instability and accelerated wear within the knee. Historically menisci were routinely completely excised when damaged but treatment today is focused if at all possible on meniscal preservation and reconstruction rather than resection.
Why does it occur?
Meniscal tears are very common and frequently lead to patients presenting to orthopaedic surgeons. There are 2 main types of tear: acute and degenerative. In younger patients meniscal tears can often occur as a result of sports injuries potentially in combination with ligament tears. In this setting the most common mechanism of injury is twisting on a loaded flexed knee causing sheer force within the meniscus leading to an acute tear.
With age, as part of the wear and tear process, the fibrocartilage of the meniscus becomes less robust and more susceptible to injury with only minor trauma. Often degenerative meniscal tears can occur without any obvious precipitating incident or from a fairly insignificant event such as getting up from a squatted position or twisting to get in and out of a car.
What are the symptoms?
The symptoms of meniscal tears vary dependent upon the pattern of tear within the cartilage. The main symptoms associated with meniscal tears are:
- Knee pain. Often felt around the joint line towards the front or back of the knee on the side of the torn cartilage.This can be worse with twisting or squatting movements.
- Swelling.Meniscal tears prompt the knee to produce synovial fluid leading to an effusion or liquid on the knee.
- Instability.Meniscal tears can catch within the knee joint leading to a feeling of giving way or locking.Certain patterns of meniscal tear can lead to an inability to fully straighten the leg.
How is it diagnosed?
Often your treating doctor will be able to form an opinion as to the likelihood of you having a meniscal tear from your history and examination findings which classically show swelling and tenderness along the joint line around where the meniscal cartilage sits. Normally the presence of a meniscal tear will be confirmed with an MRI scan and this will also give your surgeon some indication as to the pattern and location of the tear which will help with planning the best treatment for your knee.
How is it treated?
Many meniscal tears can be treated non-operatively with rest and analgesia. This is particularly so for degenerative meniscal tears where there may also be wear and tear arthritis within the knee co-existing. It is normally recommended in this setting that a period of rest of up to 3 months is taken to see if the symptoms will settle of their own accord without intervention.
If non-operative management fails for degenerative meniscal tears or in certain types of acute tear where leaving it alone would be detrimental for the knee joint, arthroscopic surgery is recommended. Dependent on the tear pattern, location and the patients age, treatment of the meniscal tear will either involve repair using internal sutures or resection of the torn fragment which is catching in the knee joint. There are pros and cons to each of these approaches and the rehabilitation for each procedure is slightly different. Your treating surgeon will discuss with you in detail the type of tear that you have and therefore the best course of action in your particular circumstances.