Osteoarticular Transfer (OATS)

Articular cartilage is a white, glistening layer, which covers the bone on each side of the joint. The smooth cartilage surface is approximately 3/8 of an inch thick and has very low friction. Articular cartilage damage in the knee is relatively common. When it is focal, and isolated, it generally is a result of an injury. Articular cartilage surfaces have little potential to regenerate themselves. The loss of cartilage can lead to pain, swelling, and limited function. Running, cutting, and jumping may be difficult when articular cartilage damage affects the weight-bearing surfaces of the knee. Occasionally, popping and snapping can occur but are nonspecific. Examination may be nonspecific and only reveal joint line tenderness. Joint swelling, or “water on the knee” can also be present and cause some degree of stiffness particularly with flexion. Plain x-rays are generally normal if the cartilage defects are relatively small. An MRI is able to more accurately determine the size and area of the missing cartilage. Nonsteroidal anti-inflammatories, along with strengthening exercises may be sufficient to minimize pain. When conservative measures fail to alleviate symptoms, minimally invasive arthroscopic surgery may be an appropriate option. When the size of the defect is 1 cm² to 2-1/2 cm², the best option is often to transfer an intact plug of bone with an attached cartilage cap from a less significant area of the knee. A corresponding sized hole is drilled into the defect and the composite bone/cartilage plug is inserted to create a new surface. This procedure is often called a “mosaicplasty”. 1 to 3 plugs, 6 – 8 mm in diameter may be necessary to fill the defect. A 6-week period of limited weight bearing is necessary to allow the plugs to begin to heal. Full recovery may require 5-6 months and generally results in good overall pain relief.

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