The two most common diseases of the knee that may indicate the need for replacement:

  • Osteoarthritis
  • Rheumatoid Arthritis


Osteoarthritis of the knee is a disease which wears away the cartilage that covers and lubricates the ends of the bone to provide natural, comfortable movement. The damaged cartilage can cause pain and stiffness in the knee that will gradually get worse during daily activities. When osteoarthritis is most severe, all the cartilage will be damaged or worn away and there will be bone-on-bone contact. Patients with osteoarthritis can develop bone spurs, or osteophytes, around the joint, further limiting motion. Osteoarthritis is a common, degenerative disease, and although it most often occurs in patients over the age of 50, it can occur at any age, especially if the joint is in some way damaged.


Osteoarthritis of the knee is a condition commonly referred to as wear-and-tear arthritis. Although the degenerative process may accelerate in persons with a previous knee injury, many cases of osteoarthritis occur when the knee simply wears out. Some experts believe there may exist a genetic predisposition in people who develop osteoarthritis of the knee.


The first and most common symptom of osteoarthritis is pain in the knee area during weight-bearing activities such as walking. People with knee pain usually compensate by limping, or reducing the force on the arthritic knee. As a result of the cartilage degeneration, the knee loses its flexibility and strength. Finally, as the condition worsens, the pain may be present all the time, even during non-weight-bearing activities.

Rheumatoid Arthritis

Unlike osteoarthritis, which is a wear-and-tear phenomenon, rheumatoid arthritis is a chronic inflammatory disease that results in joint pain, stiffness, and swelling. The disease process leads to severe, and at times rapid, deterioration of multiple joints, resulting in severe pain and loss of function.


Although the exact cause of rheumatoid arthritis is unknown, some experts believe that a virus or bacteria may trigger the disease in people having a genetic predisposition to rheumatoid arthritis. Many doctors think rheumatoid arthritis is an autoimmune disease in which the synovial tissue of the joint is attacked by one's own immune system. The onset of rheumatoid arthritis occurs most frequently in middle age and is more common among women.


The primary symptoms of rheumatoid arthritis are similar to osteoarthritis and include pain, swelling, and the loss of motion. In addition, other symptoms may include loss of appetite, fever, energy loss, anemia, and rheumatoid nodules (lumps of tissue under the skin). People suffering from rheumatoid arthritis commonly have periods of exacerbation, or flare-ups, where multiple joints may be painful and stiff.