A swollen knee occurs when excess fluid accumulates in or around your knee joint. A medical specialist may also refer to this condition as knee joint effusion. Some people have called this condition “water on the knee.”
A swollen knee may be the result of trauma, overuse injuries, or an underlying disease or condition which is determined by obtaining a sample of the fluid to be tested for infection or disease. Removing some of the fluid can also help reduce the pain and stiffness associated with the swelling.
Swelling is the result of a condition, not a condition itself. Until the underlying cause of the knee swelling is determined, appropriate treatment cannot begin.