What is a traumatic meniscus injury?
Each knee has two menisci. The medial meniscus sits between the tibia and the femur in the part of the knee closest to the midline (middle) of the body. The lateral meniscus sits between the tibia and femur in the part of the knee furthest away from the midline. The meniscus serves the important function of transmitting forces across the knee evenly when performing the weight-bearing activity. Due to their crescent shape and the fact that they are triangular in cross-section, they allow the rounded part of the bottom of the femur to fit better on the flat part of the top of the tibia. In addition, the meniscus helps to maintain the stability of the knee, improves lubrication of the knee, and absorbs some of the forces when performing weight-bearing activity.
There are two broad types of tears: Traumatic and Degenerative. Traumatic tears occur when there is a twisting or hyperflexion (deep bend) injury to the knee. These occur when playing sports such as football, skiing, squash or netball.
What are the symptoms of a traumatic meniscus injury?
The symptoms from a torn meniscus can be similar whether traumatic or degenerative. Usually, there is swelling and well-localised pain in the knee. The pain is made worse by twisting or squatting motions. Sometimes a fragment of the torn meniscus can displace inside the knee in such a way as to “lock” the knee. This can be thought of as being similar to something being caught in the hinge of the door, stopping it from moving.
How is it diagnosed?
A clinical assessment is very important, followed initially by an examination. An MRI scan will be performed to confirm the diagnosis.
What are my options for treatment?
Because the meniscus has a poor blood supply that comes from the periphery of the meniscus, it has poor healing potential. This means that it is unlikely to heal on its own. In addition, because the knee movement will move the injured meniscus, the environment of the knee is not conducive to healing.
The British Association for Surgery of the Knee (BASK) has very clear guidelines on who should and should not have an operation on their meniscus. When the meniscal tear is merely causing pain, then a period of physiotherapy plus injections is recommended for the first three months, followed by reassessment. An operation may be suitable at that point.
Some meniscal tears are amenable to repair. The factors that predict success from surgical repair of the meniscus include patient factors and factors related to the tear itself. In non-smokers who are not overweight and are under the age of 40, success rates of repair are higher.
Tears that occurred within a few weeks of the operation, that are in the periphery of the meniscus (where the blood supply is greatest) have the greatest chances of success of the repair. Studies show that repairs are successful in up to 80% of patients. In the remainder, a second operation may be necessary to remove the torn part of the meniscus that has not healed.