Osteoarthritis (OA, also known as degenerative arthritis, degenerative joint disease), is a condition in which low-grade inflammation results in pain in the joints, caused by abnormal wearing of the cartilage that covers and acts as a cushion inside joints and destruction or decrease of synovial fluid that lubricates those joints. As the bone surfaces become less well protected by cartilage, the patient experiences pain upon weight bearing, including walking and standing. Due to decreased movement because of the pain, regional muscles may atrophy, and ligaments may become more lax. OA is the most common form of arthritis. The word is derived from the Greek word "osteo", meaning "of the bone", "arthro", meaning "joint", and "itis", meaning inflammation, although many sufferers have little or no inflammation. Keeping this in mind, other closely related pathologies include pseudo-arthrosis. This is derived from the Greek words pseudo, meaning "false", and arthrosis, meaning "joint." Radiographic diagnosis results in diagnosis of a fracture within a joint, which is not to be confused with osteoarthritis which is a degenerative pathology affecting a high incidence of distal phalangeal joints of female patients.
Many people erroneously think that OA is due to wear and tear. This common misconception is due to the fact that OA typically does not present in younger people. Abnormal loading of joints due to poor posture may increase risk for OA, but only because of the abnormal loading of the joint. If a joint is loaded normally, there should be no OA - the coefficient of friction of a normal joint is frequently described as sliding ice on ice - it will go forever.
OA affects nearly 21 million people in the United States, accounting for 25% of visits to primary care physicians, and half of all NSAID (Non-Steroidal Anti-Inflammatory Drugs) prescriptions. It is estimated that 80% of the population will have radiographic evidence of OA by age 65, although only 60% of those will be symptomatic. Treatment is with NSAIDs, local injections of glucocorticoid or hyaluronan, and in severe cases, with joint replacement surgery. There has been no cure for OA, as cartilage has not been induced to regenerate. However, if OA is caused by cartilage damage (for example as a result of an injury) Chondrocyte Implantation may be a possible treatment. Clinical trials employing tissue-engineering methods have demonstrated regeneration of cartilage in damaged knees, including those that had progressed to osteoarthritis. Further, in January 2007, Johns Hopkins University was offering to license a technology of this kind, listing several clinical competitors in its market analysis.