Swollen joints happen when there's an increase of fluid in the tissues that surround the joints. Joint swelling is common with different types of arthritis, infections, and injuries. A swollen joint is a symptom of the following health conditions:
Osteoarthritis (OA). OA is the "wear-and-tear" arthritis that usually occurs with aging or after injury. With OA, there's a wearing down of the cartilage that cushions the ends of the bones. OA may cause joint swelling in those joints that bear weight over a lifetime, such as knees, hips, feet, and spine. Except for the pain in the affected swollen joint, you usually do not feel sick or tired.
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Rheumatoid arthritis (RA). RA is an inflammatory arthritis that can happen at any age -- even in young children. RA causes painful, stiff, and swollen joints. Usually, RA affects hands, feet, and knees, but it can also affect most joints and other parts of the body. RA symptoms can interfere with daily activities.
Gout. Gouty arthritis usually strikes suddenly, with severe joint pain, swelling, warmth, and redness, often in the big toe (about 50% of cases). Gout causes a painful, swollen joint that's so severe that the weight of bed sheets can cause distress.
There may also be more than one joint affected with gout.
With gout, uric acid -- a normal chemical in the body -- forms crystals that deposit in the joints, causing inflammation and pain. The crystals may also deposit in other areas to become nodules under the skin or stones in the kidney.
Infectious arthritis.Infectious arthritis or septic arthritis is the result of a bacterial, viral, or fungal infection in the tissues and fluid of a joint. Joint infection usually occurs after a previous infection in the body. The infection travels to the joint via the bloodstream from another part of the body, such as a person's skin, nose, throat, ears, or an existing wound. Within hours to days, pain, inflammation, swollen joints, and fever develop. The joints most commonly affected with infectious arthritis are the knee, hip, shoulder, ankle, and wrists. Damaged joints are more vulnerable to infection.
Common bacterial causes of infectious arthritis include Neisseria gonorrhoeae and Staphylococcus aureus. Some joint infections may be caused by more than one organism.
Joint injuries. Joint injuries can result in painful, swollen joints, and stiffness. Sometimes, joint pain can be caused by injured or torn muscles, tendons, and ligaments surrounding the joint, bursitis, tendonitis, dislocations, strains, sprains, and fractures.