Osteoarthritis (OA) of the knee is one of the most common causes of knee pain in people over the age of 30. The cause is progressive wearing away of the cartilage cushion that covers the ends of the long bones that make up the knee joint. The inflammation that accompanies this process leads to swelling and pain.

Risk factors include family history of osteoarthritis, trauma, misalignment of the knee (leg not being straight), and obesity. Initially the discomfort is described as stiffness in the knees after lying down or sitting. Going up and down stairs as well as getting into and out of a car may be difficult.

OA of the knee can also cause locking, clicking, and a "give-way" sensation in the knee.

Pain at night is also a sign of OA.

The diagnosis is established by careful history and physical examination. Physical findings include tenderness along the joint line, misalignment of the knee (either bow-legs or knock knees), and the presence of joint swelling. The hip should also be examined because hip arthritis can also cause knee pain.

Laboratory blood tests will often be ordered to rule out other causes of arthritis. In addition, the physician will often draw fluid off the knee to analyze it.

While x-rays may be ordered to determine the extent of cartilage wear, they may be normal early on in OA. Magnetic resonance imaging (MRI) is a much more sensitive method for detecting OA of the knee but is expensive.

Treatment of OA of the knee depends on the extent of symptoms. For mild pain, analgesics such as acetaminophen (Tylenol) may be sufficient. Stronger analgesics such as tramadol (Ultram) or propoxyphene (Darvon) may be more effective.

However, for those people who do not respond to acetaminophen or tramadol, the next option is low doses of non-steroidal anti-inflammatory drugs (NSAIDS). Examples of these drugs include ibuprofen (Advil), ketoprofen (Orudis) and naproxen (Aleve). These drugs may be purchased over the counter. More severe or persistent pain may require a prescription NSAID such as etodolac (Lodine), nabumetone (Relafen), dicloflenac (Voltaren), meloxicam (Mobic), and celecoxib (Celebrex). A note of caution: all NSAIDS have been associated with a slight increase in risk as far as cardiovascular events (heart attack and stroke) are concerned. They should be used with caution in patients who have a history of underlying heart disease. Also because of other reasons, they should be used with great caution in patients who have a history of ulcers or significant liver and kidney disease.

At the same time as medicines are introduced, a patient should be started on ice (ice packs) applied to the knee for 20 minutes twice a day. They should also start quadriceps setting (thigh muscle strengthening) exercises. These are exercises designed to strengthen the quadriceps muscles. The stronger these muscles are, the less pain a patient will experience.

Dietary supplements such as good quality forms of glucosamine and chondroitin may be helpful.

Injections of glucocorticoids (steroids) into the knee can be quite useful for symptomatic patients. Another type of injection- hyaluronic acid (Hyalgan, Supartz, Euflexxa, Orthovisc, Synvisc) may be indicated. Hyaluronic acid mimics the effects of the normal synovial fluid produced by the healthy knee. These injections reduce pain, provide lubrication, and may slow down the rate of cartilage deterioration.

Inserts in shoes may help with knee alignment issues and therefore can lead to pain relief.

Weight loss for patients who are obese is important. Low impact aerobic exercise (swimming, a stationary cycle, walking) accompanied by thigh strengthening and stretching are also effective for reducing pain.

Finally, braces and sleeves worn over the knee can also reduce pain that occurs with weight-bearing. Special types of braces that "unload" the part of the knee that is narrowed from arthritis can relieve symptoms in many patients.

Arthroscopy, which is a procedure where a small telescope is inserted into the knee and used to remove damaged or diseased tissue, is another potential option. Finally, patients who have pain that is associated with severe loss of cartilage from the knee may be candidates for knee replacement.