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.