Water on the knee is a common ailment that affects the health and quality of life for countless individuals each year. However, the term "water on the knee" is a bit misleading, because it is not water that is collecting on the knee and causing all that pain. Rather, it is joint synovial fluid. In small amounts, this fluid helps your knee pivot by reducing friction. However, there are several ailments and conditions that can cause excessive buildup of this fluid.
Arthritis
The type of arthritis experienced most often, osteoarthritis, is the most common cause of water on the knee. Osteoarthritis results in the deterioration of joint cartilage, which in turn causes pain and excess friction in the knee joint. This friction can cause inflammation, which results in fluid in the knee. Rheumatoid arthritis may also be the underlying cause of fluid in the knee.
Trauma
An injury to the knee also commonly causes increased fluid. A broken bone, meniscus tear or ligament tear can all lead to inflammation and swelling in the area of the knee. Overuse of the knee joint through sports, heavy lifting or other stressful activity can bring on soreness, which may also result in excessive fluid buildup.
Other Underlying Conditions
A handful of less common ailments can also contribute to fluid on the knee. An infection can result in the buildup of bacteria and synovial fluid. Cysts or tumors can cause similar reactions. Additionally, inflammation in many joints, including the knees, is a common symptom of gout and pseudogout. This inflammation leads to fluid buildup and swelling.
