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 causes 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.
There is no specific test to diagnose ankylosing spondylitis, but imaging by X-ray and MRI may show evidence of inflammation of the sacroiliac joint between the sacrum (the triangular bone at the lowest part of the back) and the ilium (the bone felt on the upper part of the hip). Some symptoms include:
Inflammatory back pain (gradual in onset, lasting over three months, with stiffness and pain that is worse in the morning and improved with movement)
Reduced mobility of the spine
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 many joints especially hands feet and knees.It can also affect other parts of the body. RA's symptoms of painful, swollen joints 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 75% 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.
Ankylosing spondylitis (AS). The key feature of AS is the involvement of the joints at the base of the spine where the spine joins the pelvis -‑ the sacroiliac joints.
Psoriatic arthritis. Psoriatic arthritis is an inflammatory joint disease that's linked with psoriasis, a skin condition. About 5% to 23% of people with psoriasis will develop psoriatic arthritis.
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 the muscles, tendons, and ligaments surrounding the joint are torn or injured. Also, painful, swollen joints may be caused by bursitis, tendinitis, dislocations, strains, sprains, or even fractures.