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Matrix-induced autologous chondrocyte implantation (MACI) is a procedure in which your own cartilage cells, known as chondrocytes, are used for knee cartilage repair. This approach can provide pain relief and improve knee function. MACI may be the best treatment option when nonsurgical treatments do not alleviate your symptoms or improve your function, you have a single area of damaged cartilage greater than 2 centimeters in diameter, and your underlying bone is healthy.

For this two-stage procedure, your doctor first performs a knee arthroscopy, in which a tiny camera is placed through a small incision in the knee to evaluate the lesion site. Using small surgical tools placed through another incision, your doctor obtains a sample of healthy articular cartilage from a non–weight-bearing portion of the knee joint. In a laboratory, your chondrocytes are grown in a culture and seeded onto a special collagen patch, known as a matrix, at a concentration of 500,000 cells per square centimeter.

During the second stage of the procedure, your doctor makes an incision in the knee to access the cartilage lesion. Your surgeon carefully removes damaged cartilage and tailors the cartilage-seeded matrix to precisely fit into the base of your knee cartilage lesion. Over time the cartilage cells migrate out of the matrix and start to regenerate tissue to fill the damaged area.

Following surgery, you participate in a carefully designed rehabilitation program to improve your knee’s range of motion and strength. People typically return to jogging 6 to 9 months after surgery and are back to athletics after 9 to 12 months.

An osteochondral autograft transfer is the transfer of healthy articular cartilage and bone from a non–weight-bearing area of the knee to fill in damage in a weight-bearing area. The procedure is typically recommended for active people younger than 50 with a small full-thickness cartilage injury from 8 to 10 millimeters in diameter.

First your doctor examines the knee joint using an arthroscope to see whether you may benefit from an osteochondral autograft transfer procedure. If your doctor finds that the damaged area is the right size and in the right location, a surgeon makes a small incision to prepare the lesion site. The surgeon removes the site of the damaged cartilage using a coring tool to create a circular hole. Next, they obtain a plug of bone and healthy cartilage from a nonessential, non–weight-bearing area of the knee with a similar coring tool. The surgeon then inserts the bone and cartilage plug into the defect area, creating a smooth joint surface.

Once the transferred bone and cartilage plug heals and you regain good knee range of motion and strength, you can return to athletic activity, typically in four to six months.

An osteochondral fresh allograft transplant treats knee cartilage defects using a tissue graft consisting of articular cartilage and bone from a donor. Your doctor may recommend this procedure if you have a full-thickness area of damage in your articular cartilage that is greater than 2.5 centimeters and that also involves the underlying bone. The procedure may also be used for smaller lesions, resulting in excellent outcomes.

Osteochondral fresh allografts are often used to treat cartilage lesions that are too large to benefit from an osteochondral autograft transfer procedure. Your surgeon may also prefer this procedure over the autograft procedure because of the size of the lesion or because of the possibility that harvesting the graft from a part of your knee could cause problems. The osteochondral fresh allograft procedure is beneficial for active individuals younger than age 50 in cases where resurfacing the joint surface is likely to reduce symptoms, improve function, and delay the onset and progression of osteoarthritis.

Once a matched graft is obtained from a tissue bank, your surgeon turns your cartilage defect into a circular hole using specialized tools placed through an open incision. They take a bone and cartilage plug from the donor graft and contour it to precisely match the damaged area. They then insert the bone and cartilage plug into the area, creating a smooth joint surface. Your surgeon closes the incision with sutures.

Once the transferred bone and cartilage plug heals and you regain good knee range of motion and strength through a physical therapy program, you should be able to return to athletic activity in about six months.