The operation is performed to stimulate repair of articular surface damage in the knee which has been worn away or damaged by direct injury resulting in a defect in the surface. Normally, the joint consists of a layer of smooth articular cartilage covering the bone ends providing an almost frictionless articulation. Once damaged the joint surface has unfortunately very little intrinsic capability to repair itself but it is possible to stimulate a form of repair using the microfracture technique.
Small “pick” holes are made in the end of the bone, using a sharp awl, approximately two to three millimetres deep and spaced every five to six millimetres. This allows for the marrow part of the bone to effectively grow onto the joint surface. This bone marrow ‘super clot’ contains specialised stem cells which can then form a new joint surface. It is expected that the repair tissue will gradually mature and improve over six to nine months from surgery.
Approximately 60 – 70% of patients note a significant improvement in symptoms of pain and function, depending on the amount of damage and intended activity. Results are best when the area of damage is small and when the area of damage is surrounded by normal articular cartilage.