Cartilage (joint surface) damage is serious as cartilage heals poorly, and damage may be the beginning of a process leading to arthritis.
The shiny white cartilage surface of the patella is at the back of the patella, where it makes contact with the cartilage of the femur as the knee is bent and straightened.
Damage to the patellar cartilage is often mirrored by damage to the femoral cartilage as well, and then this is referred to as 'patello-femoral' damage.
Management tends to be a combination of management of any underlying faulty mechanics and management of the joint cartilage itself.
Grades of cartilage damage
Surgeons will grade the cartilage degeneration for the record, so that they can compare any changes over time. Although there is more than one classification, the gradations are based on -
- The first stage is early joint damage with softening which the surgeon can feel while probing. This is chondromalacia. There is no break in the integrity of the cartilage, but it is clearly unhappy. It may be associated with pain and crunchy noises in the knee.
- The next step is when the surface begins to break up, but the bone itself still has a covering of cartilage. There may be fissures (cracks) or fronds (crabmeat).
- Then the bits start to break off and float into the joint. At this stage the process may accelerate due to the damaged surfaces giving off enzymes which themselves are destructive. The lining of the joint (synovium) sometimes becomes inflamed.
- Eventually the underlying bone becomes exposed, and the cartilage is unable to heal across the gap without assistance.
- The irritated bone tries to heal by itself, but in a deranged way, pushing up edges of bone at the joint surfaces and in the notch where the cruciate ligaments lie. These are called 'osteophytes' ('bone mushrooms') and they can restrict the joint's movement and damage the ligaments.
- The degeneration then often progresses to the menisci and they too start to degenerate.