Articular Cartilage Disorders
Articular cartilage is a white, glistening layer, which covers the bone on each of the gliding surfaces in a mobile joint. The smooth cartilage surface is approximately 3/8” thick, has very low friction, and cushions the joint during function. Weight-bearing joints (hip, knee, and ankle) are more subject to cartilage injury that those of the arm and shoulder. A direct blow or twisting injury to the knee for example, may result in a crush of the cartilage or in some cases, actually detach and dislodge a segment of cartilage from the underlying bone. Pain and swelling along with occasional catching symptoms are often present. Running, cutting, and jumping are often difficult and painful when cartilage damage affects the joints of the leg. When the articular surface wear progresses, degenerative arthritis results and can lead to pain with weight bearing, swelling, and stiffness. While an examination and X-rays may be suggestive, an MRI is often necessary to accurately diagnose damage to the cartilage surfaces of the joint. Unique to articular cartilage is the inability to heal itself to any significant extent. When symptoms of pain and swelling are unmanageable, surgery may be indicated. Normal leg alignment is a pre-requisite for treating focal cartilage defects. Treatment is usually dependent on the size and location of the defect. For defects 1 cm2, small holes are drilled into the bone, which allows bleeding, and the formation of scar cartilage (microfracture). Medium-sized defects are often managed by transferring composite bone and cartilage plugs from a separate, less essential area of the joint (osteochondral transfer – OATS). Large or multiple areas of cartilage loss may require harvesting a small amount of normal cartilage from your knee, growing the cells in culture and then transplanting them into the sites of missing cartilage (autologous chondrocyte implantation).