Damage or degeneration to the joint surface cartilage or articular cartilage in a joint can result in arthritis. Wear of the cartilage may be severe and result in an area of bare bone.
Area of cartilage damage down to bare bone on femoral condyle.
Probe is on a flap of cartilage pealing off of bone.
If the area of bare bone is isolated and there is good cartilage surrounding it, Microfracture surgery can be helpful. Microfracture is a procedure meant to release Mesenchymal Stem Cells (MSCs) from the bone marrow to allow the formation of fibrocartilage in an area of bare bone on the surface of a joint. These cells along with blood from the bone marrow create a clot that fills a defect in the articular (joint surface) cartilage. Eventually, due to the ability of these cells to form tissue of various kinds based on the local environment within the body, the area of bare bone is covered with fibrocartilage. Fibrocartilage is a mixture of fibrous tissue and cartilage best thought of as a scar cartilage. It is not as durable as articular cartilage, but it is thought to be of benefit structurally helping stabilize the edges of the cartilage defect and helping with shock absorption.
Cartilage flap removed and area prepared for microfracture
It is an arthroscopic procedure performed by using a small pick to create holes in the bone and allow blood and the MSCs from the bone marrow to come to the surface. This clot and MSC mixture eventually forms a patch of fibrocartilage to cover the area of bare bone. The results of the surgery have been reported to be 60 – 95% successful over the first four and one half years, although the results deteriorate over time. The advantages of the procedure are that it is easy to perform, can be done arthroscopically, does not require special instruments, and it does not preclude other procedures latter on.
Microfracture completed with bleeding from microfracture sites
Rehabilitation following microfracture surgery depends on how large an area of bare bone there is and what part of the knee is involved – if it is a weight bearing area or not. In general, if a microfracture is performed on a weight bearing area, crutches are used for 6 - 8 weeks. If it is not in a weight bearing are such as the kneecap (patella) or grove for the kneecap (trochlea), crutches may be used for a brief period with weight bearing as tolerated. Sometimes a CPM (Continuous Passive Motion) machine may be used. This moves the knee slowly and passively to stimulate the ingrowth of fibrocartilage. Many insurance companies do not provide coverage for a CPM for more than 2 weeks though studies show that it is helpful when used for 6-8 weeks.
Return to impact activities/sports may occur as soon as 4-6 months, but may take as long as 18 months.