Rheumatoid arthritis primarily affects the small joints of the hands, wrists, and feet, but it can spread to nearly every joint in the body and even damage organs like the lungs, heart, and eyes. Unlike osteoarthritis, which wears down cartilage through mechanical use, RA is an autoimmune disease where the immune system attacks joint tissue directly, and that same inflammatory process can reach well beyond the joints themselves.
Hands, Wrists, and Feet Come First
The joints most frequently involved are the middle knuckles of the fingers (the ones between your fingertip joints and your large knuckles), the large knuckles at the base of each finger, and the wrists. In the feet, the joints at the base of the toes are common early targets. Swelling in the hand knuckles is one of the most recognizable early signs of the disease.
RA follows a distinctive symmetrical pattern. If your right hand is affected, your left hand usually is too. This mirror-image involvement is one of the features that helps distinguish RA from other types of arthritis, which tend to show up unevenly or on just one side.
What Happens Inside the Joint
The immune system’s target in RA is the synovium, a thin membrane that lines each joint and produces the fluid that keeps it lubricated. In RA, this lining becomes inflamed and thickens dramatically. Over time, the inflamed tissue forms a destructive layer called pannus, which is packed with immune cells and sits right at the boundary between the synovium, cartilage, and bone. Pannus tissue produces enzymes that actively eat into cartilage and erode bone. This is why untreated RA doesn’t just cause pain; it permanently reshapes joints.
These changes can begin early. Synovial thickening and immune cell buildup have been documented in patients with as little as six weeks of symptoms, sometimes even in joints that don’t yet feel painful.
Elbows, Knees, Shoulders, and Ankles
As the disease progresses, larger joints often become involved. Elbows, knees, and ankles are commonly affected, and swelling in these joints is usually easy to see and feel. The shoulders can also be an early site. About 12.6% of people with RA have shoulder involvement at the time of diagnosis, though it’s rarely the only joint affected at onset.
Older adults are more likely to experience an acute onset that involves both small and large joints simultaneously, rather than the gradual small-joint pattern more typical in younger patients.
The Cervical Spine
After the hands and feet, the cervical spine (the neck) is the second most commonly involved region. Radiographic studies estimate that 43 to 86% of RA patients develop some degree of cervical spine involvement, sometimes within two years of diagnosis. The most common symptom is neck pain, particularly at the base of the skull, reported by 40 to 88% of RA patients.
Cervical involvement in RA is more than routine neck stiffness. Inflammation can loosen the ligaments that hold the top vertebrae in place, leading to instability. Some people describe a sensation of their head “falling forward” during flexion, sometimes with an audible or palpable clunk. In more advanced cases, the unstable vertebrae can compress the spinal cord, causing weakness, numbness in the limbs, or difficulty with balance and coordination. Headaches at the back of the skull are common too, occurring in 60% or more of patients with upper cervical instability, due to compression of nerves that pass between the first and second vertebrae.
Notably, RA does not typically affect the lower back. If you have low back pain, that’s more likely related to a different condition.
Lungs and Airways
Lung disease is one of the most significant ways RA reaches beyond the joints. Some degree of pulmonary involvement shows up in 60 to 80% of RA patients, though much of it remains subclinical, meaning it appears on imaging but doesn’t cause noticeable symptoms.
The main forms of lung involvement include interstitial lung disease, where inflammation and scarring develop in the tissue surrounding the air sacs. This occurs in up to 30% of patients, and nearly half may have early, silent changes visible on high-resolution CT scans. Bronchiectasis, a condition where the airways become permanently widened and prone to infection, may be present in 30 to 50% of patients on detailed imaging. RA can also inflame the lining around the lungs (the pleura), causing pleurisy or fluid buildup in up to 20% of cases, though only 3 to 5% of those patients develop obvious symptoms like cough, chest pain, or shortness of breath.
Heart and Blood Vessels
Pericarditis, inflammation of the sac surrounding the heart, is a recognized complication of RA. The chronic systemic inflammation that drives the disease also accelerates cardiovascular disease more broadly, increasing the risk of heart attacks and strokes independent of traditional risk factors like cholesterol or blood pressure.
In a small percentage of patients, RA can directly damage blood vessels, a condition called rheumatoid vasculitis. This can affect small, medium, or occasionally large vessels, leading to a range of problems: small dark spots near the fingernails (nail fold infarcts), skin ulcers, nerve damage causing numbness or weakness in the hands and feet, and in severe cases, reduced blood flow to the toes or fingers. Rheumatoid vasculitis is more common in people who have had RA for many years and have high levels of inflammatory markers.
Eyes
Eye involvement is a well-documented extra-articular feature of RA. The most common problem is keratoconjunctivitis sicca, or severe dry eye, which results from immune-mediated damage to the tear glands. This overlaps with a related condition called Sjögren’s syndrome, which many RA patients develop.
More concerning is scleritis, inflammation of the white outer coat of the eye, found in about 2% of RA patients. It causes deep, boring eye pain and redness and can, in its necrotizing form, threaten vision. Episcleritis, a milder inflammation of the tissue just above the sclera, occurs in about 5% of patients and is usually less serious. RA can also cause corneal changes and, rarely, inflammation in the retinal blood vessels.
Skin and Nervous System
Rheumatoid nodules are firm lumps that form under the skin, most often on the elbows, forearms, and fingers. They’re found almost exclusively in people who test positive for rheumatoid factor and are one of the hallmark physical signs of established RA.
Nerve involvement can happen through several routes. Swollen joints can compress nearby nerves, with carpal tunnel syndrome being a classic example in RA. Vasculitis can also damage peripheral nerves directly, causing burning pain, numbness, or weakness in the hands and feet. In the cervical spine, compression of the spinal cord or nerve roots can produce symptoms ranging from tingling in the arms to difficulty walking.
Whole-Body Symptoms
Because RA is a systemic disease driven by widespread immune activation, it produces effects that aren’t tied to any single organ. Persistent fatigue is one of the most common and most disabling symptoms, often present even when joints are relatively quiet. Low-grade fever, unintentional weight loss, and a general feeling of being unwell are common during flares. Muscle weakness and loss of muscle mass can develop over time, both from the inflammatory process itself and from reduced activity due to joint pain.
Extra-articular organ involvement, including the heart, lungs, eyes, skin, and nervous system, is present in 10 to 20% of patients overall and is more frequent in those who are seropositive, meaning they test positive for rheumatoid factor or anti-CCP antibodies. This is one reason aggressive early treatment matters: controlling the underlying inflammation protects not just the joints but the entire body.