Joint pain affects roughly one in five American adults, and the causes range from simple overuse to chronic inflammatory conditions. Figuring out why your joints hurt starts with paying attention to the pattern: which joints are involved, when the pain is worst, how long stiffness lasts, and whether you’ve noticed swelling or redness.
Wear-and-Tear Arthritis
Osteoarthritis is the most common reason joints hurt, especially after age 50. It happens when the cartilage cushioning the ends of your bones gradually breaks down, leaving bone surfaces with less protection. The joints most often affected are knees, hips, hands, and the lower back.
A hallmark of osteoarthritis is pain that worsens with activity and improves with rest. You might notice stiffness when you wake up or after sitting for a while, but it typically loosens up within a few minutes of moving around. The condition tends to develop gradually over months or years, starting as an occasional ache before becoming more persistent. Weight plays a significant role here: every pound of body weight places four to six pounds of pressure on each knee joint, which is why even modest weight loss can meaningfully reduce knee pain.
Inflammatory and Autoimmune Causes
Rheumatoid arthritis works very differently from osteoarthritis. Instead of cartilage wearing down mechanically, the immune system attacks the lining of the joints, causing pain, swelling, and stiffness that worsen over several weeks or months. The most telling clue is morning stiffness that lasts an hour or longer before it starts to ease, compared to the few minutes of stiffness typical in osteoarthritis.
Rheumatoid arthritis also tends to affect matching joints on both sides of the body, like both wrists or both knees, rather than a single joint in isolation. Blood tests can help confirm the diagnosis by looking for markers of systemic inflammation and specific antibodies the immune system produces during the disease.
Lupus is another autoimmune condition that frequently causes joint and muscle pain. It affects many parts of the body at once and can produce arthritis-like symptoms alongside fatigue, skin rashes, and organ involvement. Sjögren’s syndrome, best known for causing dry eyes and dry mouth, also commonly triggers joint pain that many people don’t initially connect to the condition.
Gout and Crystal-Related Pain
Gout produces some of the most intense joint pain you can experience. It occurs when your body accumulates too much uric acid, a waste product that normally dissolves in the blood and passes through the kidneys. When levels stay elevated, needle-shaped crystals form inside a joint, triggering sudden, severe inflammation.
Flares usually strike one joint at a time, most often the base of the big toe, and can be triggered by certain foods, alcohol, physical trauma, or illness. Some medications also raise gout risk, including water pills (diuretics), low-dose aspirin, and high-dose niacin supplements. A gout flare typically comes on fast, sometimes overnight, with the joint becoming red, hot, swollen, and exquisitely tender. Over time, repeated flares can cause hard lumps of crystal deposits to develop under the skin around joints.
Overuse and Soft Tissue Problems
Not all “joint pain” actually originates inside the joint itself. Tendons and bursae sit right next to joints, and when these soft tissues become inflamed, the pain feels identical to a problem inside the joint capsule. Many people assume they have arthritis when the real issue is bursitis or tendinitis.
Bursitis involves the small fluid-filled sacs that cushion the space between bones, muscles, and tendons. When a bursa gets irritated from repetitive motion or sustained pressure, it swells and makes the joint painful to move. Tendinitis follows a similar pattern: overuse of a tendon causes it to swell, producing pain that centers on a specific joint. Both conditions are common in shoulders, elbows, hips, and knees, particularly in people who perform the same physical motions repeatedly at work or during exercise. A chronic strain, where muscles or tendons stretch or tear slowly over time, can also mimic joint disease.
The distinction matters because bursitis and tendinitis often respond well to rest, ice, and activity modification, whereas true arthritis requires a different management approach. Imaging and a careful physical exam can sort out whether the problem is in the soft tissue or the joint itself.
Infections and Viral Illness
Joint pain that appears suddenly during or after an illness is often viral in origin. A surprisingly long list of viruses can cause arthritis-like symptoms, including hepatitis B and C, parvovirus (the virus behind “fifth disease” in children), COVID-19, Epstein-Barr virus, and mosquito-borne viruses like chikungunya and dengue. The joint pain from viral infections tends to affect multiple joints at once and usually resolves on its own within weeks, though some viruses can trigger joint symptoms that linger for months.
Bacterial joint infections are less common but far more serious. A joint that becomes rapidly swollen, warm, and painful, especially with a fever, needs prompt medical attention. Bacterial infection inside a joint can cause permanent damage quickly if untreated.
Injuries and Mechanical Damage
A sprain (stretched or torn ligament) or strain (stretched or torn muscle or tendon) from a sudden injury can cause significant joint pain. Lifting something heavy, landing awkwardly, or twisting a knee during sports are classic triggers. Most sprains and strains heal with rest and time, though severe tears sometimes require more involved treatment.
A dislocated joint, where the bones are forced out of their normal position, is a medical emergency. The joint will look visibly deformed, you won’t be able to use it, and the pain is typically severe and immediate.
Patterns That Point to a Cause
Your pain pattern is one of the most useful diagnostic clues. Pain in a single joint that came on suddenly suggests gout, injury, or infection. Pain in multiple joints that developed over weeks and includes prolonged morning stiffness points toward an inflammatory or autoimmune condition. Pain that worsens gradually over months in weight-bearing joints and eases with rest is the classic osteoarthritis pattern.
Pay attention to what makes the pain better or worse, whether there’s visible swelling or redness, and how long any morning stiffness lasts. These details help narrow the list of possibilities significantly. Joint pain accompanied by swelling, redness, warmth around the joint, or fever warrants a medical evaluation, as does any pain from an injury that leaves the joint looking misshapen, unusable, or suddenly swollen.