What causes knee pain?

Knee Arthritis

If you suffer from knee pain, it’s possible you have arthritis. Knee arthritis is caused by the deterioration of cartilage in the knee joint. The two most common types of knee arthritis are osteoarthritis and rheumatoid arthritis.


Osteoarthritis is a progressive, degenerative disease in which the cartilage of the knee slowly wears away. Cartilage serves as insulation between the bones of the joint, and when the cartilage of the knee joint wears away due to osteoarthritis, the resulting pain and inflammation can be debilitating.

Your chances of osteoarthritis of the knee increase with age; the condition most often affects middle-aged and older people. Osteoarthritis may first appear between the ages of 30 and 40, though symptoms may not be present in the early stages. By the age of 70 almost everyone will have this type of knee arthritis.


The question of what causes osteoarthritis of the knee has not been answered. Prior knee injuries seem to increase the likelihood of osteoarthritis, but many people with knee arthritis have never had a serious knee injury. Osteoarthritis is the most common form of arthritis, and many people have a genetic predisposition to this chronic disease.


The primary symptoms of osteoarthritis are pain in the knee, swelling and stiffening of the knee joint. In the early stages of osteoarthritis the pain may be mainly associated with activity. As the cartilage wears away and the bones of the joint rub against each other, pain can become more severe and constant, interfering with regular daily activities and disrupting sleep.

Rheumatoid Arthritis

Unlike osteoarthritis, Rheumatoid knee arthritis involves inflammation of the lining of the joints, known as the synovium. Though less common than osteoarthritis, rheumatoid arthritis is among the most debilitating of the over one hundred forms of arthritis. Rheumatoid arthritis usually develops in middle age, but may occur in the 20s and 30s.


The exact cause of rheumatoid arthritis is unknown. It’s possible that a virus or bacteria may trigger the disease in people with a genetic predisposition to rheumatoid arthritis. Many doctors think rheumatoid arthritis is an autoimmune disease in which the tissue of the joint’s lining is attacked by the body’s immune system. It’s also possible that rheumatoid arthritis is caused by severe stress. The disease sometimes occurs after a life-changing event such as divorce, loss of a job or a severe injury.


The primary symptoms of rheumatoid arthritis include pain and swelling in the joints and difficulty moving. Other symptoms may include loss of appetite, fever, loss of energy, anemia, and rheumatoid nodules (lumps of tissue under the skin).

If you think you may have arthritis of the knee, contact your doctor for a complete evaluation and a discussion of the options available for treatment.

Click here for information on treatment options for knee arthritis

American Academy of Orthopaedic Surgeons