The cause of water on the knee is usually arthritis. When patients have knee arthritis, fluid accumulation within the joint is a common finding. Patients often find relief when the fluid is removed from the joint, but the fluid can often reaccumulate.
Traumatic injuries can also cause accumulation of either fluid or blood within the joint. For example, meniscus tears and ligament injuries can cause fluid to collect. Furthermore, tearing of small blood vessels can cause fluid to accumulate within the knee, this is commonly seen in patients with an ACL tear.
Excess fluid around the joint can accumulate in the bursa, a condition called prepatellar bursitis. While the fluid is not actually within the knee joint itself, prepatellar bursitis also causes swelling, or water on the knee.
Treatment of water on the knee depends on the underlying problem. In cases of knee arthritis, the fluid may be drained from the knee. Patients are usually given anti-inflammatory medications or perhaps a cortisone injection. Patients with severe arthritis may eventually require surgery to treat their condition. For more information on treatment of meniscus tears or prepatellar bursitis, look through the following information: