Diseases & Conditions

What is osteoarthritis?

Arthritis, which means "joint inflammation," causes joint pain and swelling. There are many types of arthritis, but osteoarthritis is the most common type. Also known as degenerative joint disease or age-related arthritis, osteoarthritis is more likely to develop as people age. Inflammation and injury to the joint cause a breaking down of cartilage tissues, resulting in pain, swelling and deformity. The changes in osteoarthritis usually occur slowly over many years, though there are occasional exceptions.

There are two main types of osteoarthritis:

  • primary: more generalized osteoarthritis that affects the fingers, thumbs, spine, hips, and knees
  • secondary: osteoarthritis that occurs after injury or inflammation in a joint

What is cartilage?

Cartilage is a firm, rubbery material covering the ends of bones in normal joints (see figure 1). It is primarily composed of water and proteins whose primary function is to reduce friction in the joints and serve as a "shock absorber." The shock-absorbing quality of normal cartilage comes from its ability to change shape when compressed, because of its high water content. Although cartilage may undergo some repair when damaged, the body does not regenerate new cartilage after injury.

Cartilage is made up of two main elements: a gel-like substance called matrix composed primarily of water and two types of proteins – collagen and proteoglycans - and cells known as chondrocytes that are contained within the matrix.

  • Collagen is a structural protein found in many tissues such as skin, tendons and bone, and is a key structural component of cartilage. Collagen provides cartilage with its strength and creates a framework for the other components of cartilage.
  • Proteoglycans are complex molecules composed of protein and sugar combinations that are interwoven in the matrix of cartilage. Their function is to trap large amounts of water in cartilage, which allows it to change shape when compressed and thus act as shock absorber.
  • Water makes up a large part of healthy cartilage. Water helps to form a "gel-like" matrix with the other components outlined, allowing it to function as the "shock absorber" for the joint. In diseases like osteoarthritis, cartilage loses a lot of its water content. This water loss diminishes protection of the joint.
  • Chondrocytes are highly complex multifunctional cartilage cells. Functions include production of collagen, proteoglycans, and enzymes involved in the maintenance of healthy cartilage. As cartilage forms, these cells migrate through the different layers of cartilage, changing as they do so by mechanisms that are not fully understood.

What causes osteoarthritis?

Primary generalized osteoarthritis affects women more than men, often occurring shortly after menopause. Most people with primary osteoarthritis have other family members who are affected by the same problem, and usually have swelling and or pain of the finger joints, base of thumbs, and knees or hips. Secondary osteoarthritis may occur in a joint that was previously injured from trauma, or after the joint has been damaged by some other cause such as infection or rheumatoid arthritis.

Although the exact mechanisms of cartilage loss and bone changes are unknown, great advancements have been made in recent years. It is likely that complex signaling processes during joint inflammation – and defective repair mechanisms in response to injury – gradually erode cartilage within the joints. Other changes cause the joint to lose mobility and function, resulting in joint pain with activity.

Who is affected by osteoarthritis?

Although most older individuals (over 60 years old) have evidence of osteoarthritis by x-ray, most have no symptoms. More than 20 million U.S. adults have symptomatic osteoarthritis. Women are three times more likely than men to develop primary generalized osteoarthritis. Because age is a risk factor, people are more likely to develop this form of arthritis as they get older.

Are there other risk factors for osteoarthritis?

In addition to hereditary factors (genes) and other forms of arthritis, several other risk factors increase the risk for developing osteoarthritis, including other hereditary disorders, obesity, and injuries to or around the joint.

  • Heredity plays a role in osteoarthritis as individuals born with other diseases are more likely to develop osteoarthritis. Examples include conditions associated with increased joint laxity (being "double-jointed"), some dysplasias (abnormal growths of bone and cartilage) and Paget’s disease (a type of inflammation in bone that occurs in older people).
  • Obesity is a risk factor for osteoarthritis of the lower extremity and spine. Being overweight also may accelerate the rate of development of osteoarthritis. Maintaining ideal body weight or losing extra weight is important for those at risk.
  • Injuries (such as those occurring in many athletes) contribute to the development of osteoarthritis. An injury that results in abnormal stress on a joint is another important risk factor for osteoarthritis. Overuse injuries are more controversial as many people who have similar lifestyles do not develop osteoarthritis. However repetitive trauma – which may result from overuse – does increase that risk.
  • Other conditions that may lead to the development of osteoarthritis include peripheral neuropathies (diseases of the nervous system) and neuromuscular disorders that put abnormal stress on the joint.

How do I know if I have osteoarthritis?

Unlike other types of arthritis, the pain from osteoarthritis usually develops gradually over many months or years. Often it increases with activities that put a lot of stress on the joint, such as running or prolonged walking. Morning stiffness (usually lasting less than 20-30 minutes) is not a prominent symptom. Pain and joint swelling tend to increase slowly over time. Sometimes, especially in more advanced disease, a sensation of crunching or grinding may be noticed in affected joints.

Your doctor or health care provider can usually tell if you have osteoarthritis by listening to your symptoms and examining your joints. Occasionally, x-rays are needed to make sure there is no other reason for the pain. Magnetic resonance imaging (MRI) is generally not needed except in unusual circumstances or in cases when a cartilage tear is suspected. There are no blood tests that diagnose osteoarthritis. If a joint is particularly swollen, a doctor may need to drain fluid from that joint. Tests can be performed on the fluid to look for clues for other types of arthritis.

Osteoarthritis does not cause fevers, weight loss, or very hot and red joints. These features suggest some other condition or type of arthritis.

How is osteoarthritis treated?

There is no cure for osteoarthritis. The disease usually is managed by a combination of several treatments, including:

  • medications
  • supplements (also known as nutraceuticals)
  • exercise
  • hot and cold packs
  • physical, occupational, and exercise therapy
  • weight loss, and
  • supportive devices such as crutches, canes, braces and shoe inserts.

Surgery may be helpful to relieve pain when other treatment options are ineffective or have been exhausted.

The goals of treatment are to:

  • Decrease joint pain and stiffness and delay progression
  • Improve mobility and function
  • Increase patients’ quality of life

The type of treatment regimen prescribed depends on many factors, including the patient’s age, overall health, activities, occupation, and severity of the condition.

Medications

Unlike other forms of arthritis where great advances have been made in recent years, progress has been slow in osteoarthritis. Unfortunately, no medications are available today that have been shown to reverse or slow the progression of osteoarthritis.

Medications may be prescribed to decrease the pain caused by osteoarthritis. Pain-relieving medications include acetaminophen, aspirin and other salicylates, non-steroidal anti-inflammatory drugs (NSAIDs), and stronger pain medications such as codeine. Other medications in the form of creams, rubs, or sprays may be applied over the skin of affected areas to relieve pain.

Although many of these medications are available in over-the-counter preparations, individuals with osteoarthritis should talk to a health care provider before taking the medications. Some medications may have dangerous or unwanted side effects and/or may interfere with other medications being taken.

Acetaminophen is usually the first recommended treatment, as it tends to have fewer side effects than some other medications. Drug trials in osteoarthritis research clearly show that many patients prescribed NSAIDs do not tolerate them. Health care providers can prescribe agents that may be more suitable or tolerable such as non-acetylated salicylates.

Exercise

Exercise is important to improve flexibility, joint stability, and muscle strength. Regimens such as swimming, water aerobics, and low-impact strength training are recommended. These have been shown to decrease the amount of pain and disability that osteoarthritis sufferers experience. Excessively vigorous exercise programs are best avoided, as they may increase arthritis symptoms and potentially hasten the progression of the disease. Physical therapists or occupational therapists can provide appropriate and tailored exercise regimens for individuals with osteoarthritis.

Hot and cold therapies

Hot and cold treatments may provide temporary relief of pain and stiffness. Such treatments include a hot shower or bath and the careful application of heating or cooling pads or packs.

Supportive devices

Supportive or assistive devices help decrease stress on affected joints. Bracing and other supports may help to stabilize damaged joints. However, devices should be used sparingly and under the instruction of a health professional such as a therapist, physician, or other health care provider. Excessive reliance on some supports can lead to muscle wasting, which may compound the problem. Shoe lifts or inserts and canes or crutches may be helpful to take pressure off certain joints and improve body and gait mechanics.

Weight control

Since obesity is a risk factor for osteoarthritis, keeping your weight in check may help prevent osteoarthritis. Weight loss in overweight persons who have osteoarthritis has been shown to reduce stress and the amount of pain experienced in weight-bearing joints.

Surgery

When osteoarthritis pain cannot be controlled with these or other methods and when it interferes with participation in normal activities, surgery may be an option. Surgery is usually reserved for those individuals who also have significant deformities that are visible on examination or x-rays. Several types of techniques can be employed, including joint replacement, fusion, or attempts at restoration. Although not without risk, joint surgery today can be very effective at restoring some function and reducing pain for appropriate individuals. Under the best of circumstances, though, surgery cannot return the joint to its normal state. Artificial joints do not have all the motion of a normal joint.

Alternative medicine

Alternative medicine nutraceuticals and supplements are compounds that are available without a prescription and are not licensed by the FDA as drugs. They include nutritional supplements, some vitamins, and other compounds sometimes referred to as "natural." "homeopathic," or "alternative" therapies. It is important to recognize that many of these are no more or less "natural" than many prescription medications and are potentially just as dangerous. However, some compounds – particularly glucosamine and chondroitin – have shown some promise in treating osteoarthritis. It is important to emphasize that because the market for these compounds is less regulated, there is no guarantee that what is on the label is exactly what is in the bottle.

Glucosamine and chondroitin

Glucosamine and chondroitin are components of normal cartilage. They are most widely available as sulfate compounds. While some clinical trials (particularly in osteoarthritis of the knee) show they may have pain-relieving properties, others have not. Exactly how they work (if they do) remains unclear. There is no strong scientific evidence supporting the claim that they build bone and cartilage.

These nutritional supplements are available in pharmacies and health food stores without a prescription. Trials showing efficacy have used doses of 1200-1500 mg daily. As this market is less regulated than the food and drug market, many preparations exist and the actual quantity of ingredients may vary. At least initially, glucosamine and chondroitin appear to be safe and well-tolerated. Whether they have a true impact in the management of osteoarthritis remains to be seen.

Other supplements and treatments

Many other supplements and treatments have been claimed to be effective in treating osteoarthritis. Rigorous scientific evidence is needed to substantiate claims of efficacy, and many health supplements are lacking that evidence. Fish oils have some anti-inflammatory activity, but these oils have been studied more extensively for rheumatoid arthritis. Talk to your doctor before using any supplements or treatments.

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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 4/20/2010…#5599


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