Osteoarthritis is one of the most common chronic diseases affecting the elderly and is a progressive, disabling disease that occurs when many risk factors, such as old age, obesity, and trauma, act in concert to stimulate a series of pathophysiologic processes within the joint tissue. The most common signs and symptoms of osteoarthritis are fever, swelling, pain, stiffness, and limitation of motion in the affected joints. These manifestations vary widely, depending on the location of the joint and the severity of the disease. Osteoarthritis can affect any synovial joint, but primarily affects large, weight-bearing joints, such as the hip and knee, and is characterized by progressive destruction of articular cartilage. It is commonly believed that osteoarthritis begins in the articular cartilage and eventually spreads to the subchondral bone and synovial tissue. However, there is a contrary view that osteoarthritis begins in the subchondral bone and is a disease of the subchondral bone. Although the origin of the disease is controversial, there is now consensus that osteoarthritis accumulates not only the articular cartilage, but also the synovial, subchondral, and periarticular tissues.