Cartilage Repair / Restoration

The type of surgery depends on the size and location of the defect as well as the age of the patient. The different cartilage restoration procedures are listed below, but all begin with a knee arthroscopy. This is a minimally invasive procedure that involves making two small incisions (roughly 0.5 inch each) in the front of the knee joint. These small portals allow a camera to enter the joint for visualization of anatomic structures and to better evaluate the size and location of the defect as well as the surrounding cartilage.

Chondroplasty: If the cartilage injury is not full-thickness, the cartilage that has become loose or is starting to flake off can be cleaned up with a small shaving device. Only the loose cartilage is removed.

Cartilage repair: If there is bone attached to the loose cartilage piece, and in some cases where there is minimal bone attached, the cartilage fragment can be reattached with absorbable pins using arthroscopic instruments.

Microfracture: With arthroscopic instruments, the loose cartilage in the defect is cleaned out with a small shaving device. Sharp borders are created along the margin of the defect. The bone at the base of the lesion is lightly debrided and then a small-pointed instrument called an awl is used to create small holes in the bone to release the body’s stem cells. These stem cells are contained in a blood clot that forms over the defect and turn on signals to form a type of cartilage called fibrocartilage over the exposed bone. This procedure is recommended for smaller lesions (<2 cm²) and is completed arthroscopically.

Osteochondral Autologous vs. Allograft Transfer (OATS): Osteochondral means a plug of cartilage with bone. In this procedure, a portion of the cartilage and bone is harvested from one area of the knee that is less important and transferred to the area where the cartilage has been damaged and is causing pain. The patient’s own tissues can be used (autograft) if the cartilage injury is smaller (<4 cm2) and has better outcomes in athletes compared to microfracture. For larger lesions (>4 cm2), a bone/cartilage plug from a size-matched cadaver knee (allograft) is recommended. This procedure is the best procedure for patients in whom the underlying bone is also affected. This procedure is usually completed through an approximately 4-inch incision to open up the knee after the knee arthroscopy is completed.

Minced juvenile or dehydrated cadaver (allograft) cartilage: The cartilage defect is first prepared by removing the loose cartilage and creating a sharp vertical border on the perimeter of the defect. Next, cartilage from a young cadaver is minced, or cartilage from an older cadaver is processed, then inserted into the cartilage defect. A special glue is used to hold the cartilage in place. The growth factors in the allograft tissue and the debridement of the bone at the base of the lesion stimulate the body’s healing response. This surgery can be completed arthroscopically, but it often requires an approximately 4-inch incision to open up the knee after the knee arthroscopy is completed.

Matrix-associated autologous cartilage implantation (MACI): This procedure involves two parts. The first part is a diagnostic arthroscopy to obtain more accurate measurements of the cartilage injury and to harvest a strip of cartilage from a part of the knee where the cartilage is less important. The cartilage is sent to a lab where the cartilage is processed and the cartilage cells are expanded, then stored for later use. The second part of this procedure involves making an approximately 4-inch incision in the front of the knee to open the joint. The cartilage defect is prepared by removing the loose cartilage and creating a sharp vertical border on the perimeter of the defect. The cartilage cells expanded in the lab are embedded in a scaffold membrane that is then sized and secured in position with a specialized glue.

• For all cartilage restoration procedures, the surgery is most often performed under general anesthesia with a nerve block. Alternatively, procedures can be performed with a nerve block, spinal anesthetic, and sedation.
• This surgery is usually outpatient, which means the patient will be able to go home the same day.
• Surgery typically lasts 1-1.5 hours.
• Patients will be fit for a brace at an appointment.
• The brace will be placed on the patient prior to waking up from anesthesia.
• The incisions will be closed with absorbable suture with dressings that can usually be removed 2-3 days after surgery.
• The brace will need to be worn locked in full extension all of the time, including at night, but may be removed for hygiene purposes and unlocked at least three times a day for knee range of motion.

Knee range of motion is a critical part of the healing response for all cartilage procedures. For all procedures, there is a period of protected weightbearing to prevent damaging the cartilage that is trying to heal. For cartilage procedures that involve the undersurface of the patella or underlying groove in the femur, patients may place full weight on the leg almost immediately after surgery as long as the knee is kept fully straight with the knee brace. For cartilage procedures that involve the ends of the femur bone, patients typically are not able to place full weight on the leg for 6-8 weeks. Physical therapy is typically started 2 weeks after surgery and is continued for 3-4 months after surgery. Full recovery for most cartilage restoration procedures is 6 months.

• For simple cartilage debridement, patients may immediately ambulate on the operative extremity and gradually increase activities as tolerated without restrictions.