All joints require joint fluid to provide adequate lubrication and reduce friction during movement. However, a number of ailments can result in the excess buildup of fluid on the knee. This excess fluid often contains miniscule crystals, bacteria and blood, which can aggravate nearby tissue and lead to short- or long-term pain. To reduce excess fluid and alleviate pain, it is important to understand the root cause of fluid on the knee.
Arthritis
Osteoarthritis is the most common cause of fluid on the knee. Osteoarthritis is often a result of the aging process and the breakdown of joint cartilage. This lack of cartilage causes inflammation in the joint, which results in fluid on the knee. Rheumatoid arthritis can result in similar effects. Causes of arthritis include genetics, age, weight and extensive strain.
Trauma
Traumatic injuries to the knee can also result in fluid on the knee. Injuries may include broken bones, a torn meniscus or ligament tear. Athletes are particularly prone to a torn anterior cruciate ligament, or ACL, one of the four main ligaments in the knee. Overuse of the joint can lead to fluid buildup.
Other Causes
Arthritis and trauma are the most common causes of fluid on the knee. However, other potential causes of fluid on the knee include infection, gout, cysts, pseudogout, bursitis and tumors. Obesity can also cause excess strain on the knee, which can lead to the buildup of fluid on the knee.
