The ends of the femur, tibia, and undersurface of the patella (kneecap), the knee bones, are capped with a smooth surface, which is called articular cartilage. Cartilage protects the ends of bone; it can withstand a significant amount of impact and is significantly smoother than ice, which allows smooth motion in the knee joint. An articular cartilage injury (or “chondral” injury), may occur following a twisting injury to the knee, a direct blow to the knee, or wear and tear as a one ages. Many patients can be treated successfully with a combination of activity modification and other non-surgical options, such as a focused physical therapy program. Other patients with persistent symptoms or larger defects may require surgery.
In those patients with a damaged area of cartilage who require surgery, Dr. Keller may recommend stimulating new cartilage growth with stem cells. This technique is called “marrow-stimulation,” “microfracture,” or “nanofracture.” During the procedure, Dr. Keller uses a minimally-invasive technique with an arthroscope (surgical camera) and first cleans the damaged area of cartilage. Dr. Keller then carefully measures the dimensions of the damaged area. If the area of damage is relatively small, Dr. Keller will use a device to penetrate the bone underneath the damaged cartilage and create small holes. By creating small holes in the bone, Dr. Keller allows stem cells to migrate to the surface of the bone and form a new cartilage layer. Dr. Keller prefers to use a very thin, sharp instrument to create these tiny holes (nanofracture technique). In the past, orthopaedic surgeons used a larger instrument (an awl) to create the holes (microfracture technique). Following surgery, the immature stem cells can mature over several months into cartilage cells and produce a new layer of cartilage.
Following surgery, patients are placed in a hinged brace that is locked straight. Dr. Keller recommends no weight-bearing for six weeks in the brace. When the patient is sitting or lying down, Dr. Keller encourages knee range of motion exercises with the brace removed. Dr. Keller also recommends intermittent icing and straight leg raises to strengthen the quadriceps muscles. Dr. Keller recommends starting formal physical therapy one week after surgery. Physical therapy focuses on reducing swelling in the knee, restoring full range of motion, and eventually, restoring strength to the knee. Most patients can start weight-bearing on the affected leg six weeks after surgery, depending on the location of the defect. Most patients start cutting activities and sporting activity approximately 4-6 months after surgery.