Articular cartilage is the hard, slippery ‘gristle’ that covers the ends of the thighbone, shinbone and the back of the kneecap. It can be torn by a bad fall, slow damage after a knee injury, general wear and tear or poor blood supply to the joint. Cartilage does not naturally repair itself, and once torn or damaged, fragments of the cartilage may break off, or the damaged surface may cause catching and locking.
More severe cartilage-related problems can be treated with microfracture (see below). Other cartilage surgical procedures include and
The inflammation as a result of torn or damaged cartilage can be painful and the sensation of catching and locking can make activities difficult.
The history and physical exam are usually enough to make a diagnosis. X-rays are taken to rule out fractures and an MRI scan may be used to confirm the tear.
If the damage to the cartilage is severe, microfracture can be the best way of stimulating healing.
During the operation, the poor quality cartilage surrounding the severely damaged area will be cleared away, leaving a crater in the cartilage. The bottom of the crater is then drilled or abraided (like sanding) to produce bleeding from the underlying bone – which helps the development of a substance called fibrocartilage. Although not as good as the original articular cartilage, fibrocartilage is smoother and better than bare bone.
If the operation is performed on a weight-bearing part of the knee, you will have to use crutches for 6-8 weeks to allow the new cartilage to develop properly. If the operation is on the back of the kneecap or the adjoining bone, you will be able to walk normally but will have to avoid putting any pressure through a bent knee (i.e. going up and down stairs, walking on steep slopes, squatting etc) for 6-8 weeks. Activity should be gradually increased after that, under the supervision of a physiotherapist. It could be 9-12 weeks before everyday activities become completely comfortable. The damaged area goes on developing for months after surgery, so certain sports may not be advisable during that period.