Osteoarthritis or Rheumatoid Arthritis? How to Tell
Arthritis is a broad term for joint inflammation, but there are many kinds, starting with the two most common: osteoarthritis (OA) and rheumatoid arthritis (RA). Both OA and RA involve joint pain and damage, but they’re very different diseases. “Rheumatoid arthritis is a disease of the immune system,” says Clifton Bingham, M.D., a rheumatologist and director of the Johns Hopkins Arthritis Center in Baltimore. “Osteoarthritis is mechanically driven.” More people have OA than RA—30 million versus 1.3 million—and the way they’re diagnosed and treated are very different. Learn more about how to tell these two chronic conditions apart.
OA Is “Wear-and-Tear” Arthritis
OA is the breakdown of a joint, says Bill Robinson, M.D., chief of immunology and rheumatology at Stanford Health. It starts when the cartilage—the elastic slippery material that protects the ends of the bones in a joint from rubbing together—begins to thin. Changes in the cartilage can affect the whole joint, triggering inflammation in the synovial membrane (the lining surrounding the joint) and surrounding tissue, says Dr. Robinson. Eventually, the cartilage may wear completely away, and bone rubs against bone.
RA Is a Systemic Disease
RA is an autoimmune disease in which the immune system misfires and targets the synovial membrane, attacking it as if fighting off an infection, says Dalit Ashany, M.D., rheumatologist at the Hospital for Special Surgery in New York City. As a result, the synovial membrane becomes thickened and inflamed—much more inflamed than it would get with OA, notes Dr. Ashany.
OA Affects Weight-Bearing Joints (Plus Hands)
If you experienced any trauma or injury to a joint when you were younger, it can develop OA years later, says Dr. Robinson. But the most common joints affected are the weight-bearing joints of the knees, hips, and spine, plus the hands—usually the fingertip joint or middle finger joint, or the base of the thumb. In the hips and knees, OA is usually asymmetrical, affecting one side or the other, says Ali Askari, M.D., division chief of rheumatology with University Hospitals in Cleveland.
RA Starts in the Hands and Feet, Then Hits Larger Joints
RA starts most often in the small joints of the hands or feet, and later spreads to larger joints like knees, ankles, elbows, hips, shoulders, or the neck. In the hands, RA may target the wrist or finger knuckles (the bottom and middle knuckles, not the top joint). In the feet, it often occurs in the joints connecting feet to toes. Meanwhile, RA never involves the spine, except for the cervical spine (the neck), he adds. Another telltale sign of RA: It’s usually symmetrical, affecting the same joint on both sides of the body.
OA Symptoms Include Joint Pain
With OA, disintegration of cartilage triggers the release of chemicals that cause pain, says Dr. Askari, but usually not much redness, warmth, or swelling. (If you notice enlargement in your finger knuckles, that’s likely a bony growth, not swelling, says Dr. Askari. ) The pain may feel “achy” or “throbbing” and typically acts up with movement, getting worse toward the end of the day, says Dr. Askari. Many OA patients also experience joint stiffness after waking up in the morning, or after sitting for prolonged periods, but that usually fades within 30 minutes, says Dr. Ashany.
RA Has Joint Pain—Plus Much More
While RA pain can feel achy, it’s also typically accompanied by signs of severe inflammation, like redness, heat, and swelling, says Dr. Ashany. Because RA affects the immune system, inflammation levels are much higher compared with OA, she says. That’s also why morning stiffness (which happens with RA, too) takes longer—up to an hour—to go away. And because RA is a systemic disease (inflammatory mediators are released into the blood and can travel throughout the body), many people with RA also experience fatigue and general malaise, says Dr. Askani. “That’s not the case with osteoarthritis,” he adds.
OA Creates Bone
Bones react to the damage of OA by releasing cells called osteoblasts, responsible for the formation of new bone, says Dr. Robinson. This may eventually lead to bony protrusions—or osteophytes. “These result in a joint that’s no longer shaped and contoured normally,” says Dr. Robinson. They can form along any joint with OA—knee, hip, spine, base of the thumb, or knuckles (called Heberden’s nodes at the top finger knuckle, and Bouchard’s nodes at the middle knuckle). Most bone spurs don’t cause pain, but they can alter the biomechanics of your joint, leading to more stress and exacerbating the arthritis.
RA Erodes Bone
RA, on the other hand, is marked by the presence of osteoclasts, cells that cause bone erosion, says Dr. Bingham. Severe or untreated RA can cause bones to wear away and joints to shift, leading to permanent deformities over time. Still, this typically only happens in severe or untreated RA—and can be prevented through early diagnosis and proper treatment.
OA Is Diagnosed With X-rays
Both OA and RA require you to give a medical history and undergo a clinical exam for diagnosis. But for diagnosing OA, X-rays are also important, says Dr. Ashany. X-ray images can show if the space between the bones is becoming narrower, a sign of cartilage loss. And they can reveal the presence of those bony growths called osteophytes. Magnetic resonance imaging (MRI) may also be used to detect more detailed changes in the cartilage and surrounding tissues, says Dr. Askari.
RA Is Diagnosed With Blood Tests
Several lab tests are useful for confirming RA, says Dr. Bingham. For instance, up to 80% of people with RA have elevated blood levels of specific auto-antibodies (antibodies gone wrong—they mistakenly target a person’s own cells) namely, rheumatoid factor and anti-CCP. Other tests can measure the inflammatory markers in the blood and in the synovial fluid of the affected joint—the higher the inflammatory cell counts, the more likely it is to be RA (or another inflammatory disease). “In osteoarthritis, those blood tests are not elevated,” says Dr. Bingham, “because it is not a primary disease of the immune system.”
OA Treatments Are Largely About Lifestyle and Relieving Pain
Two of the most important treatments for OA are exercise and weight loss, says Soo Kim, M.D., medical director of Johns Hopkins Musculoskeletal Center in Baltimore. By strengthening the muscles surrounding the joint, more stress gets distributed onto those muscles, and less of it lands on the joint, says Dr. Kim.
To manage the pain, acetaminophen (Tylenol) or nonsteroidal anti-inflammatory drugs (ibuprofen) can help. Topical agents (NSAIDs or capsaicin) can be applied over the joint. And for severe pain, steroid or hyaluronic acid injections may help, Dr. Kim says.
RA Treatments Are Disease-Modifying Drugs
While OA meds can only treat symptoms, RA meds can actually slow the progression of the disease—even put it into remission—by tamping down on the overactive immune system, says Dr. Askari. In fact, if you catch RA early enough, there’s a good chance it will have little impact on your life, he adds. RA treatment usually starts with disease-modifying anti-rheumatic drugs (DMARDs)—the most common is methotrexate—which work by interfering with pathways in the immune system that lead to inflammation. If you don’t get the results you want from that, you may move on to more targeted DMARDs like biologics or JAK inhibitors.