Cartilage Replacement in the Knee

Articular cartilage covers the ends of bones in joints throughout the body. Normal cartilage is smooth allowing easy gliding of the joint. When cartilage is injured, the smooth surface can become rough. Cartilage is unable to heal or replace itself. Occasionally the cartilage injury is severe and there is complete loss of cartilage resulting in exposed bone. Sometimes called OATS or Mosaicplasty osteochondral grafting is a method of treating cartilage injuries that expose underlying bone. Osteochondral grafts

replace both the articular cartilage on the surface and the underlying bone. The tissue can come from other parts (typically knee) of the patient’s body (called osteochondral autograft) or from a tissue donor (osteochondral allograft). These techniques are commonly used in the knee but can be used in other joints.

The injured area of cartilage is identified and a core of the injured cartilage and the underlying bone is removed in a method similar to coring an apple. A replacement core made up of cartilage and bone from another site in the knee (autograft) or a tissue donor knee (allograft) is then made to fit into the hole. The replacement core is gently tapped into place until it lines up with the surrounding tissue. It acts as a pressfit. No screws or other devices are typically needed to hold the replacement core in place since it fits tightly. Frequently it can be performed all arthroscopically.

Patients can usually start to bear weight within 4-6 weeks of surgery. Activity is gradually increased with return to sport typically occurring after 6-9 months.

Patients often recover very well from both of these procedures. One advantage of these techniques is the ability to replace both cartilage and bone with similar tissue. There are limitations to the amount of tissue that can be taken from within a patient’s own knee so larger areas of cartilage loss may not be best for this approach. A potential concern with the use of donor tissue is the very low risk of disease transmission (like a blood transfusion). Although these techniques are new to have data on how well patients recover in the long term, it has been seen that these patients frequently do very well.

Meniscus Tears

The meniscus is the soft rubbery bumper cushion that sits between the thigh bone and the leg bone. There are two menisci in the knee; a medial (inside) and a lateral (outside) meniscus. These structures act as shock absorbers that decrease the stress seen by the articular cartilage found on the end of the thigh bone and leg bone. Meniscus injuries are quite common and occur in patients of all ages. Arthroscopic surgical treatment of a meniscus injury is the most common orthopaedic surgical procedure done in this country. An injury can occur as a result of squatting, turning or twisting during almost any activity.

Once the meniscus is torn, symptoms like locking, clicking, and catching may occur. In addition, patients will frequently notice swelling in the knee. The pain will be localized along the joint line on the inside or the outside of the knee depending on the tear. The diagnosis is made based upon a history and physical exam and frequently special tests. X-rays are usually normal. If there is some question regarding the diagnosis, an MRI can be obtained to confirm a tear. Most tears remain symptomatic and will ultimately require treatment if they interfere with activities of daily living or sports and recreation activities.

90% of the time, the appropriate treatment is arthroscopy to remove the torn fragments rather than

repair. Often the meniscus cannot be repaired due to the lack of blood supply, which prevents healing factors from getting to the area of injury even when repaired by stitches. Arthroscopic meniscal debridement is one of the most common procedures performed in orthopedics. It is typically very successful in decreasing symptoms and allowing patients to return to their normal activities. The fact that the patient has torn the meniscus increases their risk of arthritis over the next 15 to 20 years. Removing the torn fragments does not increase this risk, but merely decreases the symptoms from the tear.

Recovery from an arthroscopy to remove the torn meniscus is relatively short. It is a minimally invasive outpatient surgery with typically 2 to 3 small puncture wounds to perform the surgery. The patient will typically be weight bearing as tolerated, but he/she may need to use crutches for a few days following the surgery. Swelling typically improves during the first week. Patients with sedentary jobs can return within one to two days. More physical laborers may take longer to recover. Patients typically return to sports or exercise by 4 to 6 weeks following a short period of physical therapy. Future blogs will describe meniscus repair and review the research we are currently involved with at Washington University Sports Medicine regarding meniscus repair.