Osteoarthritis

Osteoarthritis is a chronic disorder of cartilage (the connective tissue that cushions and protects the surface of bones where they meet to form joints), bones, and some of the tissues that surround joints. Osteoarthritis is sometimes called degenerative arthritis. Osteoarthritis results in pain, stiffness, deformity, and loss of function.

Osteoarthritis is the most common type of arthritis and is very common in old age. Indeed, osteoarthritis affects most people to some degree by age 70. Whereas some people with osteoarthritis experience only annoying aches and pains, others are significantly disabled by it. A number of therapies can help relieve pain and improve joint function. For those with the most vexing problems, surgical replacement of joints relieves symptoms but poses risks.

Causes

Osteoarthritis is caused in part by wear and tear on the joints. However, use alone does not lead to arthritis. Joints that have been injured or that bear the stress of an inordinate amount of weight (as occurs in obesity) are especially susceptible to the effects of wear and tear. After arthritis begins to develop, the joints sustain further damage as the person continues to use them, particularly the joints in the shoulders, hips, knees, and lower back.

Osteoarthritis may also be caused in part by an abnormality in the way joint cartilage is formed, which causes it to swell and crack. Ultimately, the surface of the cartilage becomes pitted, and tiny cavities develop in the bone beneath the cartilage. In addition, bony outgrowths or protrusions (spurs) may form. Alternatively, the entire end of the bone may enlarge irregularly. Sometimes, outgrowths and bony enlargement occur together in the same joint.

Symptoms

Symptoms usually develop gradually. At first, only one or a few joints are affected, such as those of the fingers, base of the thumbs, neck, lower back, big toes, hips, or knees. Pain often increases when the joint is used to perform work, such as lifting or bearing weight. The joint may become stiff from lack of use but usually loosens up within 30 minutes of use. Thus, many people experience more pain when they start to move; once they are in motion, the pain decreases.

Nonetheless, affected joints tend to become increasingly damaged and painful over months and years. In addition, the supporting ligaments (tough fibrous cords that connect bones) may stretch, making the joint increasingly unsteady. Alternatively, a joint's degree of movement (range of motion) may be reduced.

Bony outgrowths may press on nerves or on blood vessels, resulting in further pain or in impaired blood flow to tissues supplied by the blood vessels.

A grating or creaking sound (crepitus) may be heard when large joints (for example, the knees) are moved. Also, joints can become enlarged and deformed (giving rise, for example, to the knotty, gnarled appearance of the finger joints often referred to as Bouchard's and Heberden's nodes). In addition, fluid accumulation (effusion) in large joints may cause swelling.

Diagnosis

A doctor diagnoses osteoarthritis on the basis of the typical symptoms, a physical examination, and x-rays of the joints. X-rays may show bone enlargement and narrowing of the space between the bone surfaces at the joint. However, x-rays are of limited usefulness in the early stages of osteoarthritis because they can show damage to the bone but are unable to show damage to the cartilage, where much of the problem exists. Magnetic resonance imaging (MRI) can detect even early changes in cartilage but is too expensive for routine use. Blood tests and analysis of the synovial fluid (the normal fluid within the joints) aid in excluding other types of arthritis, such as that in gout and pseudogout.

Prevention

Little can be done to prevent osteoarthritis, but people with early-stage osteoarthritis can try to minimize further damage. Limiting the use of affected joints is advised. People who are overweight should lose weight, which reduces the pressure on weight-bearing joints (such as knee joints). Exercises that strengthen the muscles and ligaments surrounding affected joints are also recommended.

Treatment

Osteoarthritis that neither causes symptoms nor interferes with function does not require treatment. Treatment, when necessary, aims to relieve pain, improve joint function, and enable a person to perform daily activities. To meet these treatment goals, the person should inform the doctor and other health care practitioners of the precise problems that affected joints are causing. During these discussions, both short- and long-term goals of treatment should be established.

Short-term goals may include sufficient relief of pain and stiffness so as to permit increased use of the joints. Achieving such goals allows the person to gain confidence. This confidence, in turn, increases the likelihood of achieving long-term goals, such as preserving the ability to perform daily activities. Unrealistic short-term goals and expectations of treatment (for example, complete relief of pain and resumption of all activities), however, can lead to frustration and depression.

Exercise: Regular exercise, including range-of-motion, strengthening, and endurance exercises, can help reduce joint stiffness and pain, increase flexibility and strength, and prevent further damage. However, excessive exercise should be avoided. The types of exercise that can be helpful include aerobic exercise (such as walking) combined with resistance training (such as weight training) and stretching.

Exercises performed in warm water are particularly helpful, because the buoyancy of the water provides support and reduces weight on the joints. The warmth helps reduce stiffness and discomfort during movement. Certain precautions must be taken, however, when exercising in warm water. Keeping the water temperature between about 83° and 88° F prevents overheating. In very warm water (between 98° and 104° F), time spent exercising should not exceed 15 minutes. Someone should be available to help the person get into and out of the water. Using alcohol or certain drugs can make use of a pool or spa dangerous.

Physical therapy: Physical therapy, including heat therapy and cold therapy, can be helpful. Heat therapy may involve deep heat treatment with ultrasound or with diathermy—a technique of heating parts of the body with the use of high-frequency alternating electric current applied by electrodes. Cold therapy may involve the use of ice packs.

Physical therapy may include the use of other devices and procedures as well. Splints or supports (such as soft or rigid braces) can protect joints during exercise by reducing unwanted joint movement. Shoe inserts (orthotics) often reduce pain caused by walking. Although not well studied, massage therapy may relieve pain and improve joint function when performed by a trained therapist. Sitting or lying on chairs or beds that provide firm support is also advised. Adaptive aids, such as braces and canes (which assist with walking) and grippers (which assist with opening jars) may be used. Weight loss is important for people who are overweight, because too much weight places additional strain on affected joints.

Drug therapy: Drugs may be used in addition to exercise and physical therapy to relieve symptoms. Pain relievers (analgesics), such as acetaminophen, may be useful. Nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce inflammation and relieve pain. NSAIDs must be used with caution in older people, however, because these drugs pose a higher risk of side effects, such as bleeding in the digestive tract. New NSAIDs called cyclooxygenase-2 (COX-2) inhibitors (coxibs) reduce pain much like other NSAIDs but are less likely to irritate the stomach and cause bleeding. However, one of the coxibs, rofecoxib (withdrawn from the market), appears to increase the risk of heart attack and stroke after long-term use. The risk with other coxibs is being studied. Because one recent study has shown a 2.5-fold increase in cardiovascular problems with another coxib, celecoxib, current FDA recommendations are to limit use of any coxib to people at high risk of gastrointestinal bleeding, who have a history of intolerance to other NSAIDs, or who are not doing well on other NSAIDs. Caution should be taken with use of coxibs for long periods or by people with risk factors for heart attack and stroke. All NSAIDs, including coxibs, can cause kidney damage and impair kidney function.

Glucosamine and chondroitin are nutritional supplements that can be used to treat osteoarthritis. Many preparations combine the two substances. Glucosamine and chondroitin may help the body prevent further damage to cartilage and repair existing damage to cartilage. In addition, glucosamine and chondroitin help relieve the pain of osteoarthritis.

Some drugs are applied to the skin (topically) to relieve pain in underlying joints. For example, capsaicin (derived from cayenne pepper) applied directly over the affected joint may offer relief. Capsaicin is available as a cream, gel, or lotion.

When joints are swollen, joint fluid is removed to relieve pain. A corticosteroid can be injected into the joint to further reduce inflammation. However overuse of corticosteroid injections may result in damage. Hyaluronate (a component of synovial fluid) may also be injected into the joint to relieve pain; its effects may last up to several months.

Surgery: Surgery may be performed when other treatments do not relieve pain or improve joint function.

See the figure Replacing a Knee.

In joint replacement, the most common surgery performed for osteoarthritis, an abnormal joint is replaced with an artificial joint. Joint replacement is most commonly performed on the hip and knee. Replacement almost always improves range of motion and function and dramatically decreases pain. A variety of techniques and types of artificial joints are used, depending on the affected joint.

Outlook

Osteoarthritis tends to worsen steadily with time. When drug therapy is no longer effective, patients may benefit from joint replacement.