The function of a meniscus is to act as a shock absorber within the knee.  We have two menisci.  We have a medial meniscus on the inner side of our knee, and a lateral meniscus on the outer side of our knee.

Our knees witness an enormous amount of stress during daily activities.  Each step you take can place a force of 4 times your body weight across the knee.  If you are exercising or running, that stress can increase beyond that.  With a normally functioning meniscus the force of each step is spread evenly across the end of the thigh bone,  or femur to your shin bone, or tibia.

Function of a Meniscus

As you step down, a normally functioning meniscus absorbs the stress and distends or pushes outwards.  That dissipates a lot of the force put across the knee.  If there are any defects or tears in the meniscus then the function of the mensicus can be severely compromised.  If the meniscus is not functioning well, then the force across your knee is more concentrated in a smaller area.  That can lead to loss of the articular cartilage and herald the start of an arthritic process. The most common site of a mensicus tear is the posterior horn of the medial meniscus.

Even small tears of the meniscus can lead to an increase in the risk of arthritis.  There are many different types of meniscus tears.  Some are small and stable and some are large, unstable and produce a lot of pain.  A loss of a significant amount of the meniscus, either from a tear, or following surgery can result the development of osteoarthritis due to the increase in stress now present within the knee.