What is Knee Fluid?

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  • Written By: D. Jeffress
  • Edited By: Bronwyn Harris
  • Last Modified Date: 18 September 2019
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Knee fluid is a term that usually refers to the excess buildup of fluid in the knee joint that results from an injury or illness. Body joints contain small amounts of a thick, gel-like substance known as synovial fluid that helps to lubricate and protect joint tissue. In normal amounts, synovial fluid reduces friction between bones and helps to prevent erosion of joint cartilage. When a joint such as the knee is injured, the body tends to produce excessive synovial fluid in an effort to protect it. This often leads to additional problems, however, like swelling and a loss of mobility.

A buildup of knee fluid is often known as water on the knee, and can be caused by a direct injury, an infection, or an underlying disease. Trauma from a fall or a sports injury often results in intense pain, swelling, inflammation, and stiffness. In some cases, swelling and tenderness may be so severe that it is impossible to walk or even bend the knee. Conditions not related to injury, such as osteoarthritis, gout, and tumors, usually present very similar symptoms. A bacterial or viral infection can also lead to inflammation in the knee joint and prompt the body to produce excess knee fluid.


It is important for a person to seek medical help when he or she experiences water on the knee. Without treatment, an injured knee can lead to a permanent loss of mobility as well as chronic, worsening pain. A doctor typically conducts a physical examination, orders blood tests, and takes x-rays to help determine the exact causes of excess knee fluid. If tendons, muscles, or cartilage have been damaged due to an injury, the physician may suggest surgery or simply recommend resting and icing the joint. When a doctor suspects an infection, arthritis, or gout, the patient is usually prescribed specialized oral medications to help relieve pain and other symptoms.

Recurring and long-term knee fluid buildup can usually be prevented by carefully following a physician's orders. An overweight person may be instructed to start dieting and exercising to relieve tension. Athletes and other active people may need to stretch thoroughly before events and wear knee braces to provide extra support and cushioning. Individuals who are susceptible to arthritis and gout, especially older people, may need to take dietary supplements, exercise regularly, and schedule periodic checkups with their physicians to make sure that joint problems do not worsen over time.


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Post 3

@burcidi-- Are you taking anti-inflammatory medication or a pain reliever? Aspirin and a topical analgesic gave me a lot of relief when I was suffering from the same.

Post 2

@burcidi-- The swelling will go away when your knee has healed. Keep resting, and elevating it. Avoid bending your knee or doing any activity that might further irritate it.

If the swelling doesn't go away in another few days, you should see your doctor. In rare cases, the fluid might have to be drained.

I had fluid buildup in both of my knees once due to bursitis. The sacs of my knee were inflamed because I was bending my knees too much and it caused fluid on the knee. It took close to two weeks for the swelling and fluid to disappear. I rested that entire time and did not bend my knees at all.

Post 1

I fell on my knee last week and developed knee swelling and fluid buildup soon after. I've been to the doctor, nothing is broken and I've just been told to rest, put ice and elevate my leg.

It's been five days and my knee fluid looks the same as the first day. How long will it take for the fluid to go away? Can I do anything to help?

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