Rheumatoid Arthritis vs. Osteoarthritis: What’s the Difference?
- Osteoarthritis is the most common type of arthritis, affecting about 27 million people in the United States. Osteoarthritis is caused by degeneration of cartilage and is also known as degenerative arthritis.
- In contrast, rheumatoid arthritis is an autoimmune disorder caused by the immune system attacking the joints. This autoimmune process causes systemic inflammation, while in osteoarthritis, mechanical degeneration causes localized inflammation.
- Osteoarthritis commonly affects a single joint, such as one knee. Trauma, such as multiple injuries playing sports, is a risk factor for osteoarthritis.
- On the other hand, rheumatoid arthritis usually affects three or more joints, in a symmetric distribution (both wrists, both ankles, and/or the toes on both feet). Rheumatoid arthritis frequently, but not always, causes elevation in blood levels of substances that are markers of systemic inflammation such as the ESR (sed rate or erythrocyte sedimentation rate) and CRP (C-reactive protein).
- In contrast, osteoarthritis does not cause abnormal blood test results. Both osteoarthritis and rheumatoid arthritis are hereditary. For example, if a woman (or man) has osteoarthritis or rheumatoid arthritis, her/his children are at increased risk of developing the same type of arthritis.
What Are Rheumatoid and Osteoarthritis?
Rheumatoid arthritis is a chronic joint disease that damages the joints of the body. It is also a systemic disease that potentially affects internal organs of the body and leads to disability. The joint damage is caused by inflammation of the joint lining tissue. Inflammation is normally a response by the body's immune system to "assaults" such as infections, wounds, and foreign objects. In rheumatoid arthritis, the inflammation is misdirected to attack the joints. Rheumatoid arthritis is often referred to as RA.
- The inflammation in the joints causes arthritis symptoms like joint pain, stiffness, swelling, and loss of function.
- The inflammation often affects other organs and systems of the body, including the lungs, heart, and kidneys.
- If the inflammation is not slowed or stopped, it can permanently damage the affected joints and other tissues.
Rheumatoid arthritis can be confused with other forms of arthritis, such as osteoarthritis or arthritis associated with infections. Rheumatoid arthritis, however, is an autoimmune disease. This means that the body's immune system mistakenly attacks the tissues it is supposed to protect. Rheumatoid arthritis is the most common form of autoimmune, inflammatory arthritis in adults. It can also affect children.
- The immune system in rheumatoid arthritis is misdirected and produces specialized cells and chemicals that are released into the bloodstream and attack body tissues.
- This abnormal immune response causes inflammation and thickening of the membrane (synovium) that lines the joint. Inflammation of the synovium is called synovitis and is the hallmark of an inflammatory arthritis such as rheumatoid arthritis.
- As the synovitis expands inside and outside of the joint, it can damage the bone and cartilage of the joint and the surrounding tissues, such as ligaments, tendons, nerves, and blood vessels. This leads to deformity and other irregularities and loss of function.
Rheumatoid arthritis most often affects the smaller joints, such as those of the hands and/or feet, wrists, elbows, knees, and/or ankles, but any joint can be affected. The symptoms often lead to significant discomfort and disability.
Osteoarthritis (OA) is not a single disease but rather the end result of a variety of disorders leading to the structural or functional failure of one or more of your joints. Osteoarthritis is the most common cause of chronic joint pain, affecting over 25 million Americans. Osteoarthritis involves the entire joint, including the nearby muscles, underlying bone, ligaments, joint lining (synovium), and the joint cover (capsule).
- Osteoarthritis also involves progressive loss of cartilage. The cartilage tries to repair itself, the bone remodels, the underlying (subchondral) bone hardens, and bone cysts form. This process has several phases.
- The stationary phase of disease progression in osteoarthritis involves the formation of osteophytes and joint space narrowing.
- Osteoarthritis progresses further with obliteration of the joint space.
- The appearance of subchondral cysts (cysts in the bone underneath the cartilage) indicates the erosive phase of disease progression in osteoarthritis.
- The last phase in the disease progression involves bone repair and remodeling.
What Are the Symptoms and Signs of Rheumatoid and Osteoarthritis?
Although rheumatoid arthritis can have many different symptoms, joints are always affected. Rheumatoid arthritis almost always affects the joints of the hands (such as the knuckle joints), wrists, elbows, knees, ankles, and/or feet. The larger joints, such as the shoulders, hips, and jaw, may be affected. The vertebrae of the neck are sometimes involved in people who have had the disease for many years. Usually at least two or three different joints are involved on both sides of the body, often in a symmetrical (mirror image) pattern. The usual joint symptoms include the following:
- Stiffness: The joint does not move as well as it once did. Its range of motion (the extent to which the appendage of the joint, such as the arm, leg, or finger, can move in different directions) may be reduced. Typically, stiffness is most noticeable in the morning and improves later in the day.
- Inflammation: Red, tender, and warm joints are the hallmarks of inflammation. Many joints are typically inflamed (polyarthritis).
- Swelling: The area around the affected joint is swollen and puffy.
- Nodules: These are hard bumps that appear on or near the joint. They often are found near the elbows. They are most noticeable on the part of the joint that juts out when the joint is flexed.
- Pain: Pain in rheumatoid arthritis has several sources. Pain can come from inflammation or swelling of the joint and surrounding tissues or from working the joint too hard. The intensity of the pain varies among individuals.
These symptoms may keep someone from being able to carry out normal activities. General symptoms include the following:
- Malaise (a "blah" feeling)
- Loss of appetite or lack of appetite
- Weight loss
- Myalgias (muscle aches)
- Weakness or loss of energy
The symptoms usually come on very gradually, although in some people they come on very suddenly. Sometimes, the general symptoms come before the joint symptoms, and an individual may think he or she has the flu or a similar illness.
The following conditions suggest that rheumatoid arthritis is quiet, referred to as "in remission":
- Morning stiffness lasting less than 15 minutes
- No fatigue
- No joint pain
- No joint tenderness or pain with motion
- No soft-tissue swelling
People with osteoarthritis may experience the following signs and symptoms:
- Pain: Aching pain, stiffness, or difficulty moving the joint may develop in one or more joints. The pain may get worse with overuse and may occur at night. With progression of this arthritis, the pain can occur at rest.
- Specific joints are affected.
- Fingers and hands: Bone enlargements in the fingertips (first joint) are common. These are called Heberden nodes. They are usually not painful. Sometimes they can develop suddenly and are painful, swollen, and red. This is known as nodal osteoarthritis and occurs in women older than 45 years of age. Another typical joint affected is at the base of the thumb (basal thumb joint or first carpometacarpal joint). This can lead to difficulty gripping and turning keys and opening jars.
- Hip: The hips are major weight-bearing joints. Involvement of the hips may be seen more in men. Farmers, construction workers, and firefighters have been found to have an increased incidence of hip osteoarthritis. Researchers think that a heavy physical workload contributes to OA of the hip and knee.
- Knees: The knees are also major weight-bearing joints. Repetitive squatting and kneeling may aggravate osteoarthritis.
- Spine: Osteoarthritis of the spine can cause bone spurs or osteophytes, which can pinch or crowd nerves and cause pain and potentially weakness in the arms or legs. Osteoarthritis affecting the low back can lead to chronic low back pain (lumbago). Osteoarthritis in the spine leads to degenerative disc disease (spondylosis).
What Is the Treatment for Rheumatoid and Osteoarthritis?
Despite significant advances in treatment over the past decades, rheumatoid arthritis continues to be an incurable disease. While there is no cure, the goal of disease remission is frequently attainable. Treatment of RA symptoms has two major components:
- reducing inflammation and preventing joint damage and disability and
- relieving symptoms, especially pain. Although achieving the first goal may accomplish the second, many people need separate treatment for symptoms at some point in the disease.
Rheumatoid arthritis is a progressive inflammatory disease. This means that unless the inflammation is stopped or slowed, the condition will continue to worsen with joint destruction in most people. Although rheumatoid arthritis does occasionally go into remission without treatment, this is rare. Starting treatment as soon as possible after diagnosis of rheumatoid arthritis is strongly recommended. The best medical care combines medication and nondrug approaches.
Nondrug approaches include the following:
- Physical therapy helps preserve and improve range of motion, increase muscle strength, and reduce pain.
- Hydrotherapy involves exercising or relaxing in warm water. Being in water reduces the weight on the joints. The warmth relaxes the muscles and helps relieve pain.
- Relaxation therapy teaches techniques for releasing muscle tension, which helps relieve pain.
- Both heat and cold treatments can relieve pain and reduce inflammation. Some people's pain responds better to heat and others' to cold. Heat can be applied by ultrasound, microwaves, warm wax, or moist compresses. Most of these are done in the medical office, although moist compresses can be applied at home. Cold can be applied with ice packs at home.
- Occupational therapy teaches people ways to use their body efficiently to reduce stress on the joints. It also can help people learn to decrease tension on the joints through the use of specially designed splints. The occupational therapist can help someone develop strategies for coping with daily life by adapting to the environment and using different assistive devices.
- In some cases, reconstructive surgery and/or joint replacement operations provide the best outcome.
Drug approaches include a variety of medications used alone or in combinations.
- The goal of drug treatment is to induce remission or at least eliminate evidence of disease activity.
- Early use of disease-modifying antirheumatic drugs (DMARDs) not only controls inflammation better than less potent drugs but also helps prevent joint damage. Newer DMARDs work better than the older ones in long-term prevention of joint damage.
- People treated early with DMARDs have better long-term outcomes, with greater preservation of function, less work disability, and a smaller risk of premature death.
- The current approach, therefore, is to treat rheumatoid arthritis aggressively with DMARDs soon after diagnosis. Treating rheumatoid arthritis early, within three to 12 months after symptoms begin, is the best way to stop or slow progression of the disease and bring about remission.
- Ongoing (long-term) treatment with combinations of medications may offer the best control and prognosis of rheumatoid arthritis for the majority of people.
- Combinations of these medications do not usually have more severe adverse effects than one medication alone.
The medications for rheumatoid arthritis fall into several different categories. These RA medications include
- disease-modifying anti-rheumatic drugs (DMARDs),
- biologic response modifiers,
- JAK modifiers, glucocorticoids,
- nonsteroidal anti-inflammatory drugs (NSAIDs),
The overall goal of treatment is early elimination of risk factors, early diagnosis and surveillance of the disease, and appropriate treatment of pain. It's also important to help people regain their mobility. These goals may be reached through a logical approach to care, including the overlapping of treatment that does not involve medications and treatment with medication and possibly surgical management.
Treatment that does not involve medications includes education, physical and occupational therapy, weight reduction, exercise, and assistive devices (orthoses).
Initially, simple over-the-counter pain relievers such as acetaminophen are recommended, followed by NSAIDs. Prescription NSAIDs may be needed if the over-the-counter medications are ineffective. A new generation of prescription NSAIDs are the COX-2 medicines (celecoxib [Celebrex]). The COX-2 drugs have fewer reported gastrointestinal side effects but similar results compared to the typical NSAIDs.
The antidepressant duloxetine (Cymbalta) is now approved by the Food and Drug Administration (FDA) for chronic musculoskeletal pain (joint and muscle pain). This medication works on neurotransmitters in the brain that control pain perception and has been shown to decrease chronic low back pain and pain caused by knee osteoarthritis.
Surgery may relieve pain and improve function.
- Arthroscopy is the examination of the inside of a joint using a small camera (endoscope). Arthroplasty is the repair of a joint in which the joint surfaces are replaced with artificial materials, usually metal or plastic.
- Osteotomy is incision or cutting of bone.
- Chondroplasty is surgical repair of the cartilage.
- Arthrodesis is a surgical fusion of the bony ends of a joint preventing joint movement. For example, fusion of an ankle joint prevents any further joint movement of the ankle itself. This is done as a result of many years of significant joint pain resulting from a previous significant injury or severe osteoarthritis. The procedure is performed to help block further pain by preventing any further joint movement.
- Joint replacement is removal of diseased or damaged bony ends and replacement with a manmade joint composed of a combination of metal and plastic. Knee joint replacement and hip replacement are the most common. Some joints, such as those of the spine, cannot be replaced presently.
What Is the Prognosis for Rheumatoid and Osteoarthritis?
As a rule, the severity of rheumatoid arthritis waxes and wanes. Periods of active inflammation and tissue damage marked by worsening of symptoms (flares) are interspersed with periods of little or no activity, in which symptoms get better or go away altogether (remission). The duration of these cycles varies widely among individuals.
Outcomes are also highly variable. Some people have a relatively mild condition, with little disability or loss of function. Others at the opposite end of the spectrum experience severe disability due to pain and loss of function. Disease that remains persistently active for more than a year is likely to lead to joint deformities and disability. Approximately 40% of people have some degree of disability 10 years after their diagnosis. For most, rheumatoid arthritis is a chronic progressive illness, but about 5%-10% of people experience remission without treatment. This is uncommon, however, after the first three to six months.
Rheumatoid arthritis is not fatal, but complications of the disease shorten life span by a few years in some individuals. Although generally rheumatoid arthritis cannot be cured, the disease gradually becomes less aggressive and symptoms may even improve. However, any damage to joints and ligaments and any deformities that have occurred are permanent. Rheumatoid arthritis can affect parts of the body other than the joints.
The early treatment and use of DMARDs and biologic response modifiers in rheumatoid arthritis has resulted in patients experiencing more profound relief of symptoms and less joint damage and less disability over time. So the prognosis is best when treatment is started early. New treatments are on the horizon.
A single prognosis is difficult to establish because of the variety of factors influencing the disease. It also may be important to look at the particular joint involved rather than lumping all the joints together to predict the outcome. For example, the prognosis for hip osteoarthritis may be different than the prognosis for hand osteoarthritis. Symptoms may not be able to be predicted based on X-rays, because some people experience a great deal of pain with only mild osteoarthritis on X-ray, and some people experience only mild pain while their X-rays show severe osteoarthritis. But a few studies may predict joint deterioration.
Some findings suggest that the following are true:
- Narrowing of the joint space seems to be linked with deterioration of the condition.
- The presence of osteoarthritis of the hands is a predictive sign for deterioration of the knee joints.
- People with rapid progression seemed to have knee pain upon entry into clinical studies.
Future research into causes of joint pain in patients with osteoarthritis will likely lead to improved treatments. Ongoing scientific studies are encouraging and include work looking at the effects of antibodies against nerve growth factor, which seems to play a role in pain perception in those afflicted by osteoarthritis of the knees and hips.
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Rennie, N.G., et al. "Presence of Gout Is Associated with Increased Osteoarthritis Prevalence and Severity." Arthritis and Rheumatism 63.10 Oct. 2011.
McInnes, I.B., and G. Schett. "Mechanisms of Disease: The Pathogenesis of Rheumatoid Arthritis." N Engl J Med 365 (2011): 2205-2219.