Joints are places in your body where two bones come together, such as your wrists, elbows, shoulders, hips, knees, and ankles.
Joints also exist where you might not think. For example, there are joints between the many bones in your feet, hands, pelvis, and spine.
Pain in just one joint usually has different causes than pain in many joints.
At all ages, the most common cause of sudden pain in one joint is:
If you haven't been injured, the most common causes depend on your age.
Among young adults:
Among older adults:
Less common causes of pain in one joint include:
Osteonecrosis is when bone dies and collapses. Bone can die as a result of serious injury (such as a broken hip) or as a side effect of some medicines (such as corticosteroids).
See a doctor right away if you have pain in one joint and any of these warning signs:
Sudden or severe pain
Joint redness, warmth, swelling, or stiffness
Broken, red, warm, or tender skin near the joint
Signs of sudden illness other than joint pain
Chance of a sexually transmitted disease
Call a doctor after several days if you have mild joint pain that doesn’t stop on its own.
Your doctor will ask about your symptoms and health history and do a physical exam.
Doctors may do tests such as:
Tests of joint fluid—doctors take fluid out of your joint with a needle and test the fluid for signs of infection or gout
Imaging tests, usually x-rays, but sometimes MRI or CT scan
Rarely, blood tests
Doctors will treat the cause of your pain. For example, if you have a bone fracture, doctors may put your joint in a cast. If you have a joint infection, they will give you antibiotics and often do surgery to drain the infection.
Doctors may also treat your joint pain with: