Our bodies are made up of different types of cartilage and the knee joint is composed of 2 different types:

1. Articular cartilage lines the ends of the bones: the femur (thigh bone), the tibia (shin bone) and the back of the patella (knee- cap). It is designed to protect the bones against load and lubricate the joint surface to ensure it moves smoothly. Osteoarthritis involves a thinning of this structure and it starts to become rougher. This causes a reduction in the ability of the joint to tolerate load. Most of us will experience this process as we get older but not all of us suffer with the symptoms. It is still an area of extensive research.
2. The tibia is relatively flat on its surface and the femur is rounded. To improve congruency between these two structures there are 2 crescent shaped menisci which sit between the bony surfaces. This ensures that load is distributed more evenly across the joint surface. The meniscus can sustain various types of tear which can be degenerative or traumatic. In most cases symptoms caused by a meniscal tear can settle well through conservative treatment but in more severe cases the tear can cause the knee to lock which will require surgery.

Symptoms associated with cartilage damage include joint swelling and stiffness. The knee can become sore to bend and rotation tends to cause sharp catches within the joint.