Osteoarthritis (OA), also known as degenerative joint disease, is a gradual breakdown of cartilage in joints. This chronic condition can cause pain and impair movement, especially in the elderly population. Many people consider OA a natural part of aging. It occurs most often in the knees, hips, spine, hands and feet. It may be limited to one joint, but can affect several joints throughout the body.

OA is the most common form of arthritis. It affects about 14 percent of American adults, according to the U.S. government. Most of these people are over age 55, and the condition affects more women than men. Some individuals may experience only aching knees. Others are disabled by the condition, unable to walk or climb stairs without help.

The cause of OA is unknown. However, certain risk factors such as age and excess weight appear to contribute to the development of the disease. OA may also be linked to injury, stress on the joints, muscle weakness and heredity.

Pain, stiffness and reduced joint movement are the most common symptoms of OA. It often begins in one joint and may progress to additional joints over time. Diagnosis typically begins with a physical examination and may include x-rays or other imaging tests of joints.

OA cannot be cured. Treatment focuses on relieving pain and slowing the progression of the disease. It may include medications, rest, physical therapy, exercise and occupational therapy. Lifestyle changes such as weight loss and use of assistive devices may help some people. If joints are seriously degenerated and are painful, surgery to replace joints or fuse bones may be performed.

There are no proven methods to prevent OA. Practices that promote healthy joints, such as exercise and weight loss, may delay the onset or reduce the severity of the disease.

Osteoarthritis (OA) is the most common type of arthritis. It most often affects weight-bearing joints in the knees and hips, along with the hands and spine. It can cause stiffness, joint pain and reduced movement. If OA is located in the hips or knees, it can impair an individual’s ability to stand, walk, climb and engage in other physical activities.

OA occurs in the joints, where two or more bones meet. It primarily develops in the joints with the most movement, such as hips, knees, feet and hands. These joints are known as cartilaginous and synovial joints. A synovial joint capsule is a space enclosed by the bones and adjoining ligaments. The outer layer of the capsule is formed by a fibrous membrane. The inside of the capsule is lined with synovial membrane and filled with synovial fluid, which provides lubrication. The ends of the bones encased in the capsule are cushioned in soft cartilage. The cartilage and synovial fluid permit the bones to move without rubbing against each other.

Cartilaginous joints do not have a synovial cavity, but have cartilage and fibrous discs between the bones to allow some movement. The vertebrae in the spine have cartilaginous joints.

Most OA damage is the result of cartilage degeneration. Cartilage is made up of three substances:

• Collagen. A fibrous protein common in skin and connective tissue.
  
  
• Proteoglycans. Strands of protein and sugar.
  
  
• Chondrocytes. Cells that usually help cartilage development, but can release enzymes (proteins that stimulate chemical reactions) that destroy collagen and other proteins.

Changes in the interaction of cartilage tissue lead to its deterioration. Chondrocytes can produce enzymes that destroy collagen and proteoglycans. Although the origin of this enzyme disruption is unknown, outside factors, such as years of stress on the joint, may be involved.

The disrupted interaction of chondrocytes, collagen and proteoglycans eventually leads the cartilage to break down. The smooth cartilage surface wears and frays. The bone underlying the cartilage is exposed and may form bony spurs called osteophytes. With less cartilage, more exposure of bone and ragged surfaces, the joint cavity becomes smaller and joint movement becomes painful or stiff.

OA is usually defined by this degenerative process. It was previously thought that the disease involved no inflammation, despite the fact that the word arthritis means inflammation in a joint. However, some recent studies have indicated that joints severely degenerated by OA have, in fact, shown some inflammation.

Joints commonly affected by OA include the fingers, spine and the weight-bearing joints of the hips, knees and feet. It is less common in the jaw, shoulders, elbows, wrists and ankles, unless there was a separate injury or stress in the area, such as an athletic injury or trauma. Although many forms of arthritis can affect other body systems, OA remains confined to the joints.

The course of OA varies for each person. Some individuals may experience a slight ache in one joint that never worsens. Other people may have morning stiffness or pain with exercise. In some cases, OA limits mobility and restricts the abilities of joints such as the fingers and knees. Most cases of OA are primary OA, which begin with no known origin. Secondary OA occurs after injury or overuse of a particular joint, such as the knee.

OA affects about 14 percent of Americans over age 24 and 34 percent over age 64, the Centers for Disease Control and Prevention (CDC) reported in 2008. That translates to 27 million adults in 2005, up from 21 million in 1990, a reflection of the aging population.

It is important to note that OA is not the same as rheumatoid arthritis (RA), a more severe, inflammatory form of arthritis that occurs in younger people. Although both forms of arthritis cause joint pain, there are several major differences:

• OA involves degeneration of joint cartilage. RA, an autoimmune disorder, involves inflammation of the membranes lining joints.
  
  
• OA may occur on one side (e.g., in one knee). RA usually occurs symmetrically, such as in both hands or both knees.
  
  
• OA affects only the joints. RA can affect other systems in the body, including the lungs, nerves or heart.

Nor should OA be confused with osteoporosis, another condition that commonly affects elderly people. Osteoporosis is a reduction in bone mass, commonly known as "thinning of the bones," that makes bones more brittle and easily broken. OA affects joints, not bone mass.

Some people consider osteoarthritis (OA) a normal part of aging. The most common cause is the normal "wear and tear" of a joint. Mechanical stress on a joint over time may affect the enzymes (proteins that stimulate chemical reactions) in cartilage, but the exact relationship is unclear.

Some risk factors for OA have been identified. Risk factors make an individual more likely to develop a condition but do not mean the person will get the disease. In addition, people with no risk factors can still develop the disease. The most common risk factors associated with OA include:

• Age. OA usually develops after age 45 and is most common after age 65.
  
  
• Weight. Overweight or obese people are more likely to develop OA.
  
  
• Heredity. People with a family member with OA are more likely to develop the disease. Inherited bone abnormalities, such as a malformed joint or defective cartilage, may also increase the likelihood of developing OA. Even a minor difference in leg lengths, a common condition, may increase the risk of knee and hip OA, research has indicated.
  
  
• Sex. Although OA is less common before age 55, it occurs equally in both sexes in this age group. After age 55, it is more common in women than men.
  
  
• Lifestyle factors. People are more likely to develop OA when they have repetitive motion or stress on a joint from exercise or work conditions. Also, individuals who have long periods of immobilization are at risk for OA.

• Injury. Having a sports injury, such as a torn knee cartilage (meniscus injury) or a fracture near the joint, makes an individual more susceptible to OA. Knee surgeries, such as repair of a torn anterieror cruciate ligament, may increase risk of early OA. Weak muscles in the thighs may lead to the OA in the knees.

• Medical conditions. Diseases that cause a change in the structure or function of joints also increase the likelihood of OA. These include other forms of arthritis, such as rheumatoid arthritis and gout, and hemochromatosis, a condition in which excess iron can get deposited within cartilage causing destruction.
  
  
• Nerve disorders. Peripheral neuropathy, a condition that affects the nerves in limbs, may increase the likelihood of OA. Causes of neuropathy include diabetes and alcoholism.

Some research has contradicted the popular notion that cracking the knuckles or other joints contributes to osteoarthritis.

Most people who experience symptoms of osteoarthritis (OA) have joint pain, limited mobility and stiffness. Many experience stiffness when they wake in the morning, which usually lasts no more than 30 minutes. Stiffness that lasts an hour may be a symptom of rheumatoid arthritis (RA). Joints may become sore when used after periods of inactivity or after exercise. Pain that occurs during activity or exercise usually is relieved by rest.

Patients may experience crepitus, a grating, grinding or crackling sound or sensation in joints affected by OA. Crepitus can be painless or painful.

Symptoms of OA vary, depending on the joints affected. Some of the main symptoms, grouped according to joints, include:

• Fingers. May include pain, swelling or enlargement of finger joints. Bone spurs called Heberden's nodes (in end joints) and Bouchard's nodes (in middle joints) may also appear. People may experience difficulty with fine-motor movements such as picking up items or gripping a pen.
  
  
• Spine. In the spine, growths on or around the intervertebral discs may cause pain or pressure on nerves. This may be experienced as pain or stiffness in the neck, arms, lower back or legs. Pinched nerves may produce numbness in the arms or legs. As OA affects the spine, it may lead to other complications such as spinal stenosis, a narrowing of spinal canal.
  
  
• Hips. May cause pain in the groin, buttocks or thighs. Hip pain may also cause limping. OA in the hip may cause referred pain, which originates in the hip but is felt in the knee, thigh or lower back.
  
  
• Knees. May cause knee pain while moving, walking, using stairs or rising from a chair. OA in the knee may produce a slipping sensation, as if there is no support in the leg. It can also produce creaking or grating sounds when the knee moves.
  
  
• Feet and ankles. May cause pain and swelling in the feet, especially the joint at the base of the big toe. It may also cause foot pain while wearing high heel or tight shoes that was not previously experienced with those types of shoes.

For thousands of years, people have perceived a connection between the onset of arthritic pain and changes in weather (usually approaching rain). Such changes were noted as early as 400 B.C. by the ancient Greek physician Hippocrates. Although many people acknowledge a connection, the studies conducted on the phenomenon have not yielded definitive results. These studies may not be representative because they had small groups of subjects and relied on self-reporting methods. Still, many individuals with OA report an increase amount of pain and stiffness before or during a change in weather.

Diagnosis of osteoarthritis (OA) begins with a review of the patient’s medical history. Focus will be placed on any familial arthritic conditions, previous injuries or surgeries and general use of the joints. A pain assessment may also be used to help identify the nature and severity of the condition. A physical examination that concentrates on the areas of complaint may be completed by a rheumatologist (specialist in arthritis and other inflammatory diseases) or other physician.

The physician will examine the joints and surrounding areas for:

• Pain or tenderness
• Swelling or stiffness
• Reduced range of motion or flexibility
• Instability or difficulty bearing weight
• Crepitus (grating or crackling sound or feeling)
• Bony lumps, nodes or growths

Most diagnostic examinations where OA is suspected will include imaging studies, such as x-rays, MRI (magnetic resonance imaging) or a bone scan.

Although x-rays and MRI are good indicators of damage to joints, the degree of damage may be unrelated to the intensity of a patient’s symptoms. Physicians use the studies to look for:

• Bony outgrowths (osteophytes)
• Narrowing of the joint capsule
• Hardening or formation of cysts

Laboratory tests cannot diagnose OA. However, blood tests may be used to rule out other forms of arthritis and diseases if needed. These tests may include:

• Rheumatoid factor (RF) test. May indicate rheumatoid arthritis (RA) or other autoimmune conditions.
  
  
• Erythrocyte rate (ESR or sed rate). An elevated level in this blood test indicates inflammation, but can be caused by many forms of inflammation or infection. It may be combined with the physician's clinical findings to confirm conditions such as polymyalgia rheumatica.
  
  
• C reactive protein test. An elevated level of this protein produced by the liver suggests an inflammatory disease, such as RA.

Other blood tests may indicate the presence of uric acid, a sign of gout, or the presence of a genetic marker that is seen with some other forms of arthritis.

In some cases, a biopsy or synovial fluid analysis may be completed. These tests may identify or rule out other conditions but cannot diagnose OA.

The combination of findings from lab tests, x-rays and a physical examination may provide a physician with enough information to diagnose OA.

Because osteoarthritis (OA) cannot be cured, treatment concentrates on controlling pain, improving function and slowing the degeneration of joints. Knowledge about the likely course of OA may help people preserve or improve function of joints and learn ways to manage the condition.

Many OA treatment methods may also be used to slow the progress of joint degeneration or prevent further damage. For instance, many lifestyle factors can be adjusted for OA, including getting adequate amounts of sleep, resting when experiencing fatigue, avoiding activities that place stress on the joints and wearing appropriate shoes and clothing.

Regular exercise can help maintain muscle tone and improve flexibility and range of motion for joints. Research indicates that exercise may slow progression of OA and strengthen cartilage in the joints.

Although it is uncertain whether weight loss slows the progression of OA in affected joints, it can alleviate joint stress and pain. One recent study of overweight people with knee OA indicated that every pound shed yielded a four-pound reduction in force on the knees during every step, which could slow the progression of the disease. An analysis of several studies concluded that overweight people with OA could reduce disability by losing only 5 percent of their weight.

OA patients may also benefit from physical therapy or occupational therapy. Physical therapy can improve flexibility, strength, endurance and range of motion. All of these factors may help reduce the symptoms of OA and prevent further deterioration. Physical therapists can also evaluate and provide assistive devices to help with joint stability and movement. These devices can include braces or splints, canes, walkers and electric power lifts.

Occupational therapy can help OA patients with their activities of daily living (ADLs). Occupational therapists (OTs) can evaluate the patient and provide exercises and recommendations on ways to execute tasks such as dressing, bathing and household chores. OTs can provide the patient with adaptive equipment to make activities easier, especially for arthritic hands. Examples of this equipment include reachers, jar openers, adapters to make dressing easier and larger grips for utensils. In addition, an OT can conduct a home assessment to recommend changes (e.g., grab bars in the shower, raised toilet seats) that will make everyday activities easier for individuals with OA.

The following OA treatment methods may also be used for symptomatic relief:

• Heat, cold and water therapies. A physician, physical therapist or occupational therapist can indicate which kind of therapy should be used for treatment. Heat (thermotherapy), such as ultrasound therapy, relieves pain, muscle spasm and stiffness. Cold (cryotherapy) relieves pain and may reduce swelling. Water therapy (hydrotherapy) is often combined with thermotherapy or exercise therapy. People with some medical conditions, such as poor circulation, should not use cold therapy, and conditions such as impaired sensation may rule out use of heat therapy.
  
  
• Medication. Many prescription and nonprescription medications are used for OA pain. Some of these include:
  
  
• • Nonsteroidal anti-inflammatory drugs (NSAIDs). These drugs are used to reduce pain and inflammation. They come in prescription and nonprescription forms and include gels that have demonstrated effectiveness in relieving OA pain in the knees.
    
    
  • Acetaminophen. This over-the-counter analgesic may relieve mild pain associated with OA.
    

• • Injection therapy. Hyaluronic acid is a synthetic version of the fluid in the joint capsule. A physician may inject it into joints of a patient who does not receive pain relief from noninvasive treatments. Corticosteroids may be injected in cases where OA is confined to a few joints and pain cannot be relieved with NSAIDs. The use of corticosteroid injections for OA is somewhat controversial. Physicians recommend no more than three or four injections a year for weight-bearing joints.
    
    
  • Topical analgesics. Capsaicin cream, which has the same active substance as hot chili pepper, can lessen the pain for OA patients. A newer kind of NSAID patches are available and may be of some use for pain relief if applied locally.
    
    
• Electrical therapy, such as transcutaneous electrical nerve stimulation (TENS). This treatment delivers mild electric current to the skin and stimulates nerves to interfere with transmission of pain signals. It can alleviate pain or modify the perception of pain for OA patients, especially those with knee pain.
  
  
• Supplements. Many people use supplements such as glucosamine and chondroitin as complementary and alternative therapies to help relieve the chronic pain of OA. These supplements are not medications and are not regulated by the U.S. Food and Drug Administration (FDA). The studies of their effectiveness have not been conclusive, although most evidence indicates the supplements cause no harm. A study of knee OA sponsored by the National Institutes of Health (NIH) indicated that glucosamine and chondroitin can help relieve moderate to severe pain but in general may be no more effective than a placebo (sugar pill).
  
  
• Acupuncture and acupressure. These alternative treatment methods are based on traditional Chinese practices about specific body points that control pain. Acupuncture uses needles inserted at these points. Acupressure applies pressure to the same points but does not involve needles. Studies differ on the value of acupuncture and acupressure for OA pain. Some patients with soft-tissue pain experience relief, but others report no change.
  
• Surgery. Several types of surgery can correct OA damage. Surgery is usually reserved for the most debilitating cases of OA after other treatments have proven ineffective. Types of surgery include:
  
  
• • Arthroscopy. A flexible lighted tube is inserted in a joint to remove fragments of bone or cartilage from the joint capsule. It may also be used to remove the lining of the joint capsule (synovectomy). Arthroscopy may not provide much pain relief to OA patients.
    
    
  • Corrective surgery. May be used on deformed joints and to realign bones (osteotomy).
    
    
  • Fusion (arthrodesis). Surgeons may fuse bones, usually in the spine, or in other areas where the joints are damaged but joint replacement is not an option (fingers, toes or ankle). A fused joint can bear weight but is no longer flexible.
    
    
  • Joint replacement surgery (arthroplasty). Damaged joints may be partially or completely replaced. When a joint is completely degenerated, surgeons can replace the entire joint. This is most commonly performed for the knees and hips but can also be used to treat shoulders and some other joints.

Researchers are studying many potential treatments to slow the progression of OA or reduce pain and disability. These include bioengineered implants of a patient’s own cartilage, osteoporosis treatments such as bisphosphonates and the hormone calcitonin, and injections of botulinum toxin type A (Botox).

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about osteoarthritis (OA):

1. Do I have OA or another form of arthritis?
   
   
2. What tests might I need to undergo, and what do they involve?
   
   
3. What do my test results show?
   
   
4. Will my joint pain spread to other joints?
   
   
5. What will alleviate my osteoarthritis pain?
   
   
6. What forms of exercise are safe for me?
   
   
7. Can glucosamine, chondroitin or other supplements help my osteoarthritis? Are there any supplements I should avoid?
   
   
8. Can heat therapy, hydrotherapy, electrotherapy, acupuncture or other such treatments help my pain?
   
   
9. Will physical therapy or occupational therapy prevent further deterioration?
   
   
10. Should I get assistive devices to help my mobility or adaptive equipment to help protect my joints during daily tasks?
    
    
11. Am I a candidate for surgery?
    
    
12. Is there anything I can do to prevent OA or slow its progression?
    
    
13. If I have OA, are my children more likely to get it?