Osteoarthritis (OA) is the most common disease of joints in adults around the world, affecting more often middle-aged and older people. OA is a progressive degenerative disease in which the natural cushioning between joints (cartilage) wears away. Articular cartilage is known for its specific characteristics that combine a smooth surface which enables smooth motion of the bone and the ability to withstand extreme amounts of pressures. However, cartilage has limited intrinsic healing potential; therefore once an injury occurs, it is necessary to repair the articular surface to obtain good functional outcome and to avoid subsequent cartilage degeneration. Failure to achieve cartilage restoration produces the symptomatic pain, inflammation, swelling, and stiffness, decreased ability to move and, sometimes, the formation of bone spurs.

Generally, the pain associated with arthritis develops gradually, although sudden onset is also possible. The joint may become stiff and swollen, making it difficult to bend or straighten the knee. Pain and swelling are worse in the morning or after a period of inactivity. Pain may also increase after activities such as walking, stair climbing, or kneeling. The pain may often cause a feeling of weakness in the knee, resulting in a “locking” or “buckling.” Many people report that changes in the weather also affect the degree of pain from arthritis.

The knee is affected most often, due to the load that receives daily. Contrary to popular belief, arthritis is not caused by ageing and does not necessarily deteriorate. OA is a metabolically active repair process that takes place in all joint tissues and involves localized loss of cartilage and remodeling of adjacent bone.  Several factors increase the risk of developing significant arthritis at an earlier age, such as joint trauma or overuse, ligamentous injuries or damage to the menisci of the knee that result in continuing tissue damage and symptomatic arthritis.