Arthritis can affect nearly every joint in the body, from the small bones in your fingers to the large joints in your hips and knees. But different types of arthritis target different areas, and some forms reach well beyond the joints to involve organs like the heart, lungs, and eyes. Understanding which parts of the body are at risk depends largely on which type of arthritis you’re dealing with.
Joints Hit Hardest by Osteoarthritis
Osteoarthritis, the most common form, is driven by the gradual breakdown of cartilage, the slippery tissue that cushions the ends of bones. It most frequently affects the hands, knees, hips, and spine. Weight-bearing joints like the hips and knees take extra punishment because added body weight increases the mechanical stress on those surfaces over time.
In the hands, osteoarthritis tends to settle into the base of the thumb and the finger joints closest to the fingernails, often producing bony enlargements that change the shape of the fingers. In the spine, it typically targets the lower back and neck, where decades of movement wear down the cartilage between vertebrae. Any joint can develop osteoarthritis after an injury, even joints that wouldn’t normally be high-risk, like the ankle or wrist.
Where Rheumatoid Arthritis Strikes
Rheumatoid arthritis (RA) is an autoimmune condition, meaning the immune system attacks the body’s own joint lining. It favors the small joints of the hands and feet, particularly the knuckles and the middle joints of the fingers. A hallmark of RA is symmetry: if the knuckles on your left hand are inflamed, the same knuckles on the right hand usually are too. Research shows that some joints trend toward symmetry more than others. The middle finger joints tend to mirror each other more consistently, while the large knuckles and wrist compartments are more likely to be lopsided early on, then become more symmetrical over time.
RA can also affect the wrists, elbows, shoulders, knees, and ankles. Unlike osteoarthritis, it rarely targets the lower spine. The pattern of involvement, along with blood markers, is one of the main ways doctors distinguish RA from other forms of arthritis.
The Spine and Pelvis in Ankylosing Spondylitis
Ankylosing spondylitis is a type of inflammatory arthritis that centers on the spine and the sacroiliac joints, the two joints where the base of the spine connects to the pelvis. Inflammation at these sacroiliac joints is so characteristic that imaging evidence of it is considered a major diagnostic criterion.
In the early stages, the vertebrae begin to change shape, losing their normal curve in a process called “squaring.” Over years, if the disease progresses unchecked, the vertebrae can fuse together through bony bridges that form along the ligaments of the spine. This late-stage fusion, sometimes called “bamboo spine” on X-rays, most commonly appears where the thoracic spine meets the lumbar spine or where the lumbar spine meets the sacrum. The result is a rigid spine with significantly limited range of motion. Beyond the spine, ankylosing spondylitis can also inflame peripheral joints, individual fingers and toes, and the connective tissue where tendons attach to bone.
Fingers, Toes, and Skin in Psoriatic Arthritis
Psoriatic arthritis is linked to psoriasis, the skin condition that causes scaly, inflamed patches. It has a distinctive pattern in the hands and feet. One of its hallmark forms targets the joints closest to the fingertips and toenails, the same joints that osteoarthritis favors but that rheumatoid arthritis typically skips. This overlap sometimes leads to misdiagnosis.
Another telltale sign is dactylitis, or “sausage fingers,” where an entire finger or toe swells along its length rather than at a single joint. Psoriatic arthritis also affects the fingernails and toenails, causing pitting, thickening, or separation from the nail bed. In its most severe form, called arthritis mutilans, the disease can cause devastating damage to the hands and feet, dissolving bone and collapsing joints.
The Big Toe and Other Gout Targets
Gout is caused by a buildup of uric acid crystals in a joint, and it has a strong preference for the base of the big toe. Many people experience their very first gout flare there, often waking up in the middle of the night with sudden, intense pain. The joint becomes red, hot, and so tender that even the weight of a bedsheet can be unbearable.
Gout doesn’t stop at the big toe, though. It can strike the ankles, knees, wrists, fingers, and elbows. Repeated flares over years can deposit visible clusters of crystals under the skin, called tophi, around the affected joints and even on the outer ear.
Tendons and Ligament Attachments
Several inflammatory types of arthritis don’t limit themselves to the joint capsule. They also attack the entheses, the points where tendons and ligaments anchor into bone. This inflammation, called enthesitis, is especially common in psoriatic arthritis and ankylosing spondylitis, though it can also occur in rheumatoid arthritis. Common sites include the Achilles tendon at the back of the heel, the bottom of the foot near the heel (plantar fascia), and the areas around the knee and elbow. Enthesitis can be one of the earliest signs of these conditions, sometimes appearing before obvious joint swelling does.
The Jaw
Arthritis can affect the temporomandibular joint (TMJ), the hinge that connects your lower jaw to the skull just in front of each ear. Both osteoarthritis and rheumatoid arthritis can damage this joint, causing pain while chewing, jaw stiffness, limited opening, and painful clicking or popping. Roughly 11 to 12 million adults in the United States experience pain in the TMJ region. In some cases the inflammation changes the way the upper and lower teeth fit together, and it can even contribute to ringing in the ears or dizziness.
Beyond the Joints: Organs and Systems
Rheumatoid arthritis in particular can reach far beyond the joints. The same immune dysfunction that inflames joint tissue can target the heart, lungs, eyes, skin, and blood vessels. These effects, collectively called extra-articular manifestations, tend to be more common in people with long-standing or severe disease.
In the lungs, inflammation of the lining (pleuritis) affects roughly 5 to 10 percent of RA patients. It can also lead to scarring of lung tissue, fluid around the lungs, or small airway disease. In the heart, pericarditis (inflammation of the sac around the heart) is the most common cardiac complication, but RA also independently raises the risk of atherosclerosis, heart attacks, heart failure, and valve disease. Nodules made of the same inflammatory tissue found in the joints can form on heart valves and alter their function.
The eyes are another frequent target. At least 10 percent of people with RA develop dry eyes and dry mouth from reduced gland function, a combination often linked to secondary Sjögren’s syndrome. More serious eye involvement includes scleritis, a painful inflammation of the white of the eye that can threaten vision, and episcleritis, a milder surface inflammation that usually resolves on its own.
Skin manifestations include rheumatoid nodules, firm lumps that form under the skin near affected joints, and vasculitis, an inflammation of blood vessels that can cause rashes, skin ulcers, or nerve damage in the hands and feet.