Fluid in the knee

Fluid in or around the knee joint is common. In most cases, this is a direct reaction of the body to an injury or an inflammatory reaction. The medical term is knee effusion.

How does fluid in the knee occur?

Usually, fluid in the knee is a sign that there is damage. Examples include a stretched knee ligament, a torn meniscus, a torn cruciate ligament or a kneecap out of joint. These are all examples of injuries where fluid in the knee is one of the first signs. The knee feels unstable and the pain increases with movement and loading of the knee.

Due to the fluid in the knee, bending and straightening the knee may not be possible, or not fully. The combination of fluid in the knee, warmth, redness and pain at the front of the kneecap may indicate joint inflammation or bursitis of the knee.

The combination of morning stiffness and/or creaking sounds (crepitus) when moving the knee, together with older age, points to osteoarthritis. In this condition, the quality and thickness of the articular cartilage have decreased.

How is the cause of fluid in the knee diagnosed?

The diagnosis is made on the basis of a consultation between the physiotherapist or doctor and the patient about the onset of the symptoms and several physical tests. These tests are intended to detect damage to knee ligaments, meniscus or cartilage.

In case of doubt, it may be necessary to take an X-ray or an MRI scan to determine the cause of the swollen knee. When the knee is very swollen, it often remains slightly bent. This is the ‘position of Bonnet’. This posture is the least painful and gives the swelling the most space.

To further examine the fluid in the knee, a doctor can perform a joint puncture. Using a needle, the doctor aspirates fluid from the knee, which is then examined for inflammatory markers. A joint puncture often provides immediate relief of pain, as the fluid is gone or reduced. Unfortunately, this is usually only short-lived and the fluid returns as long as the cause has not been remedied.

Treatment of fluid in the knee

To reduce the fluid in the knee, it is sensible to put less load on the knee. Taking regular rest and elevating the leg help to reduce the pain and swelling. As soon as possible, it is good to slowly build up the load again.

Once the cause of the fluid in the knee is clear, treatment starts. In the case of joint inflammation or bursitis, anti-inflammatories and rest are usually prescribed. With damage to the knee ligaments or the meniscus, an operation is sometimes necessary to restore the function of the knee.

If no operation is needed, treatment mainly consists of exercise therapy with the physiotherapist. The exercises are then aimed at strengthening the muscles around the knee. The aim is to improve the function of the knee joint.