Joint effusion refers to the abnormal accumulation of fluid within the synovial compartment of a joint. Effusion most often affects the knee, hip, elbow and ankle joints. In the knee, it is commonly called “water on the knee.”

Normal joints contain a small amount of fluid. When the joint is affected by inflammation, infection, or physical trauma to the cartilage or ligaments, extra fluid may build up around the joint, causing it to appear swollen. Other symptoms often include joint pain, redness, warmth, stiffness and decreased range of motion.

Underlying diseases and conditions that may produce joint effusion include osteoarthritis, rheumatoid arthritis, psoriatic arthritis, infection, gout, cysts and tumors.

Depending on the underlying cause of the joint effusion, one of Lancaster Orthopedic Group’s joint specialists will focus on reducing the swelling, relieving pain, improving the function of the joint, and treating any underlying illnesses. Your physician may drain and examine fluid from the affected joint to help confirm or rule out infection.

In the absence of infection, rest, moist heat or ice, anti-inflammatory medications, and/or corticosteroid injections are commonly used to treat joint effusion and prevent the fluid from building up again. Swollen joints caused by infection are treated with antibiotics and may require surgery (arthrocentesis) to draw fluid out of the joint.