Osteoarthritis research causes
by Nathan Wei, MD, FACP, FACR
Nathan Wei is a nationally known board-certified rheumatologist and author of the Second Opinion Arthritis Treatment Kit. It's available exclusively at this website... not available in stores.
Click here: Second Opinion Arthritis Treatment Kit
Information from the National Institutes of Health and the American College of Rheumatology
WHAT CAUSES OSTEOARTHRITIS?
Although osteoarthritis generally accompanies aging, osteoarthritic cartilage is chemically different from normal aged cartilage. Many experts now believe that osteoarthritis is a disorder that results from a genetic susceptibility coupled with injuries to the joint.
For years, scientists thought that osteoarthritis was simply a disease of "wear and tear" that occurred in joints as people got older. In the last decade, however, research has shown that there is more to the disorder than aging alone. The production, maintenance, and breakdown of cartilage, as well as bone changes in osteoarthritis, are now seen as a series or cascade of events. Many researchers are trying to discover where in that cascade of events things go wrong. By understanding what goes wrong, they hope to find new ways to prevent or treat osteoarthritis. Some key areas of research are described below.
Animal Models: Animals help researchers understand how diseases work and why they occur. Animal models help researchers learn many things about osteoarthritis, such as what happens to cartilage, how treatment strategies might work, and what might prevent the disease. Animal models also help scientists study osteoarthritis in very early stages before it causes detectable joint damage.
Diagnostic Tools: Some scientists want to find ways to detect osteoarthritis at earlier stages so that they can treat it earlier. They seek specific abnormalities in the blood, joint fluid, or urine of people with the disease. Other scientists use new technologies to analyze the differences between the cartilage from different joints. For example, many people have osteoarthritis in the knees or hips, but few have it in the ankles. Can ankle cartilage be different? Does it age differently? Answering these questions will help us understand the disease better.
Genetics Studies: Researchers suspect that inheritance plays a role in 25 to 30 percent of osteoarthritis cases. Researchers have found that genetics may play a role in approximately 40 to 65 percent of hand and knee osteoarthritis cases. They suspect inheritance might play a role in other types of osteoarthritis, as well. Scientists have identified a mutation (a gene defect) affecting collagen, an important part of cartilage, in patients with an inherited kind of osteoarthritis that starts at an early age. The mutation weakens collagen protein, which may break or tear more easily under stress. Scientists are looking for other gene mutations in osteoarthritis. Recently, researchers found that the daughters of women who have knee osteoarthritis have a significant increase in cartilage breakdown, thus making them more susceptible to disease. In the future, a test to determine who carries the genetic defect (or defects) could help people reduce their risk for osteoarthritis with lifestyle adjustments.
Tissue Engineering: This technology involves removing cells from a healthy part of the body and placing them in an area of diseased or damaged tissue in order to improve certain body functions. Currently, it is used to treat small traumatic injuries or defects in cartilage, and, if successful, could eventually help treat osteoarthritis. Researchers at the NIAMS are exploring three types of tissue engineering. The two most common methods being studied today include cartilage cell replacement and stem cell transplantation. The third method is gene therapy.
• Cartilage cell replacement: In this procedure, researchers remove cartilage cells from the patient's own joint and then clone or grow new cells using tissue culture and other laboratory techniques. They then inject the newly grown cells into the patient's joint. Patients with cartilage cell replacement have fewer symptoms of osteoarthritis. Actual cartilage repair is limited, however.
• Stem cell transplantation: Stem cells are primitive cells that can transform into other kinds of cells, such as muscle or bone cells. They usually are taken from bone marrow. In the future, researchers hope to insert stem cells into cartilage, where the cells will make new cartilage. If successful, this process could be used to repair damaged cartilage and avoid the need for surgical joint replacements with metal or plastics.
• Gene therapy: Scientists are working to genetically engineer cells that would inhibit the body chemicals, called enzymes, that may help break down cartilage and cause joint damage. In gene therapy, cells are removed from the body, genetically changed, and then injected back into the affected joint. They live in the joint and protect it from damaging enzymes.
Comprehensive Treatment Strategies: Effective treatment for osteoarthritis takes more than medicine or surgery. Getting help from a variety of care professionals often can improve patient treatment and self-care. Research shows that adding patient education and social support is a low-cost, effective way to decrease pain and reduce the amount of medicine used.
Exercise plays a key part in comprehensive treatment. Researchers are studying exercise in greater detail and finding out just how to use it in treating or preventing osteoarthritis. For example, several scientists have studied knee osteoarthritis and exercise. Their results included the following:
• Strengthening the thigh muscle (quadriceps) can relieve symptoms of knee osteoarthritis and prevent more damage.
• Walking can result in better functioning, and the more you walk, the farther you will be able to walk.
• People with knee osteoarthritis who were active in an exercise program feel less pain. They also function better.
Research has shown that losing extra weight can help people who already have osteoarthritis. Moreover, overweight or obese people who do not have osteoarthritis may reduce their risk of developing the disease by losing weight.
Using NSAIDs: Many people who have osteoarthritis have persistent pain despite taking simple pain relievers such as acetaminophen. Some of these patients take NSAIDs instead. Health care providers are concerned about long-term NSAID use because it can lead to an upset stomach, heartburn, nausea, and more dangerous side effects, such as ulcers.
Drugs to Prevent Joint Damage: No treatment actually prevents osteoarthritis or reverses or blocks the disease process once it begins. Present treatments just relieve the symptoms. Researchers are looking for drugs that would prevent, slow down, or reverse joint damage. One experimental antibiotic drug, doxycycline, may stop certain enzymes from damaging cartilage. The drug has shown some promise in clinical studies, but more studies are needed. Since this monograph, doxycycline's effects have proven to be minimal at best. Researchers also are studying growth factors and other natural chemical messengers. These potential medicines may be able to stimulate cartilage growth or repair.
Acupuncture: During an acupuncture treatment, a licensed acupuncture therapist inserts very fine needles into the skin at various points on the body. Scientists think the needles stimulate the release of natural, pain-relieving chemicals produced by the brain or the nervous system. Researchers are studying acupuncture treatment of patients who have knee osteoarthritis. Early findings suggest that traditional Chinese acupuncture is effective for some patients as an additional therapy for osteoarthritis, reducing pain and improving function.
Nutritional Supplements: Nutritional supplements are often reported as helpful in treating osteoarthritis. Such reports should be viewed with caution, however, since very few studies have carefully evaluated the role of nutritional supplements in osteoarthritis.
• Glucosamine and chondroitin sulfate: Both of these nutrients are found in small quantities in food and are components of normal cartilage. Scientific studies on these two nutritional supplements have not yet shown that they affect the disease. They may relieve symptoms and reduce joint damage in some patients, however. The National Center for Complementary and Alternative Medicine at the NIH is supporting a clinical trial to test whether glucosamine, chondroitin sulfate, or the two nutrients in combination reduce pain and improve function. Patients using this therapy should do so only under the supervision of their doctor, as part of an overall treatment program with exercise, relaxation, and pain relief.
• Vitamins D, C, E, and beta carotene: The progression of osteoarthritis may be slower in people who take higher levels of vitamin D, C, E, or beta carotene. More studies are needed to confirm these reports.
Hyaluronic Acid: Injecting this substance into the knee joint provides long-term pain relief for some people with osteoarthritis. Hyaluronic acid is a natural component of cartilage and joint fluid. It lubricates and absorbs shock in the joint. The Food and Drug Administration (FDA) approved this therapy for patients with osteoarthritis of the knee who do not get relief from exercise, physical therapy, or simple analgesics. Researchers are presently studying the benefits of using hyaluronic acid to treat osteoarthritis.
Estrogen: In studies of older women, scientists found a lower risk of osteoarthritis in women who had used oral estrogens for hormone replacement therapy. The researchers suspect having low levels of estrogen could increase the risk of developing osteoarthritis. Additional studies are needed to answer this question.
Genetic and Biologic Factors
Researchers report a higher correlation of osteoarthritis between parents and children or between siblings than between husbands and wives. Genetic factors are thought to be involved in about half of osteoarthritis cases in the hands and hips and a somewhat lower percentage of cases in the knee. A number of genes are under investigation that might contribute to an inherited risk.
A 2000 study identified the ank gene, which regulates pyrophosphate, a chemical that inhibits the formation of mineral deposits, and may protect the cartilage in joints. (Pyrophospate is also a substance used in tartar control toothpaste). About 60% of persons with osteoarthritis have mineral deposits in their cartilage. Researchers have suggested that mutations in the ank gene that may result in lower pyrophosphate levels in the joint, leading to accumulation of mineral deposits and arthritis.
The newly detected osteoprotegerin gene is important in regulating bone and cartilage formation. Mutations in this gene may play a role in osteoarthritis.
Muscle weakness and osteoarthritis are commonly associated. One belief for this link is that arthritic pain discourages muscle activity so that eventually the muscles weaken and atrophy (wither) from disuse. Of interest is a study suggesting that weak muscle tissue in the quadriceps is responsible for osteoarthritis in the first place. (The quadriceps are four muscles that stretch down the thigh and attach to the knee; they are responsible for leg extension.) This weakness may be due to an abnormality in the muscles themselves or in the nerves that serve those muscles. In the study, strength tests revealed that people with osteoarthritis had muscle weakness in the quadriceps even if they had no pain. However, there were no differences in signs of disuse between the legs of arthritic and nonarthritic people.
Some researchers suggest that a number of people have anatomical abnormalities, such as mismatched surfaces on the joints, which could be damaged over time by abnormal stress. Legs of unequal length or skewed feet can cause jerky movement and may induce osteoarthritis. One study reported that those whose knees bent inward (“knock-kneed”) or outward (“bow-legged”), for example, were more likely to have progressive osteoarthritis of the knee. Other research is investigating differences in cartilage and other factors that may contribute to osteoarthritis.
One large study found that by age 65, osteoarthritis developed in almost 14% of those who had had joint injuries as young adults, compared to just 6% in those without earlier injuries. What’s more, those with knee injuries were five times more likely to have osteoarthritis in the injured knee than those without injuries, and those with hip injuries were more than three times more likely to develop arthritis in the injured hip. Proper treatment of injuries, such as surgical repair of ligament tears in the knee with a strong rehabilitation process, may help to prevent the development of osteoarthritis. Injury from different sources can contribute to osteoarthritis:
Single Injury. Osteoarthritis sometimes develops years later after a single traumatic injury to or near a joint.
Repetitive Labor. Certain occupations that require repeated stressful motions (such as squatting or kneeling with heavy lifting) can also contribute to deterioration of cartilage.
High-Intensity Exercise. There has been some question about the role of strenuous exercise in osteoarthritis. Sports that definitely pose a higher risk for osteoarthritis are those that require repetitive or direct joint impact (such as football), twisting, or both (baseball pitching, soccer).
Marathon runners, however, have a relatively low rate of osteoarthritis in general. Some scientists speculate that running enhances cartilage health because the rhythmical compression of cartilage expels wastes and promotes absorption of nutrients. (One study did report a higher rate of osteoarthritis in marathon runners, which was associated with a higher intensity of impact rather than with the distance being run.)
In any case, regular and moderate exercise is important for everyone and does not increase the risk for osteoarthritis. Furthermore, many factors associated with a sedentary life--muscle weakness, obesity, and low lung capacity--are associated with a high risk for osteoarthritis.
Being overweight exacerbates osteoarthritis once deterioration begins. One major long-term study suggested there may be a causal relationship between obesity in women and osteoarthritis of the knees. In men, the association is not as strong.
Other Medical Conditions that Can Cause Osteoarthritis
Other causes of osteoarthritis include the following:
• Bleeding disorders, such as hemophilia, that cause bleeding to occur in the joint.
• Disorders such as avascular necrosis that block the blood supply near the joint.
• Complications of persistent, inflammatory arthritic conditions, particularly chronic gout, pseudogout, or rheumatoid arthritis.
• Conditions such as hemochromatosis that cause iron build-up in the joints.
Research is opening up new avenues of treatment for people with osteoarthritis. A balanced, comprehensive approach is still the key to staying active and healthy with the disease. People with osteoarthritis should combine exercise, relaxation education, social support, and medicines in their treatment strategies. Meanwhile, as scientists unravel the complexities of the disease, new treatments and prevention methods should appear. They will improve the quality of life for people with osteoarthritis and their families.
National Institute of Arthritis and Musculoskeletal and Skin Diseases
National Institutes of Health
1 AMS Circle
Bethesda, MD 20892-3675
(301) 495-4484 or (877) 22-NIAMS (free of charge)
TTY: (301) 565-2966
Fax: (301) 718-6366
NIAMS provides information about various forms of arthritis and rheumatic diseases. It distributes patient and professional education materials and also refers people to other sources of information.
American College of Rheumatology
1800 Century Place, Suite 250
Atlanta, GA 30345
Fax: (404) 633-1870
This association provides referrals to rheumatologists and physical and occupational therapists who have experience working with people who have osteoarthritis. The organization also provides educational materials and guidelines.
1330 West Peachtree Street
Atlanta, GA 30309
Call your local chapter (listed in the telephone directory),
or (800) 283-7800 (free of charge)
The foundation is a major voluntary organization devoted to supporting research on arthritis and other rheumatic diseases. The foundation publishes a free pamphlet on osteoarthritis and a magazine for members on arthritis and related conditions. It also provides up-to-date information on treatments, nutrition, alternative therapies, and self-management strategies. Chapters nationwide offer exercise programs, classes, support groups, physician referral services, and free literature.
Get more information about osteoarthritis research causes and related topics as well as...
• Insider arthritis tips that help you erase the pain and fatigue of rheumatoid arthritis almost overnight!
• Devastating ammunition against low back pain... discover 9 secrets!
• Ignored remedies that eliminate fibromyalgia symptoms quickly!
• Obsolete treatments for knee osteoarthritis that still are used... and may still work for you!
• The stiff penalties you face if you ignore this type of hip pain...
• 7 easy-to-implement neck pain remedies that work like a charm!
• And much more...
Second Opinion Arthritis Treatment Kit
Return to arthritis home page.