Baker’s cyst

A rounded swelling at the back of the knee which is often about the size of a golf ball, but can vary over time. A sensation of pressure in the back of the joint will be felt, which may go down into the calf muscle. The patient will have difficulty bending or straightening the knee joint due to pain behind the knee.

What is a popliteal cyst?
In the hollow at the back of the knee is a bursa or small sack of fluid, used to help lubricate the joint. A fairly uncommon condition is when the back of the knee joint gets swollen and causes the bursa to swell as well. Usually some underlying disorder of the knee such as a meniscus injury or arthritis can cause an increase in synovial fluid, which is the knee’s natural lubricating fluid. This then spills into the bursa at the back of the knee, causing it to increase in size and swell up, causing a popliteal cyst,  more commonly known as a Baker’s cyst.

In younger athletes the cause may be a torn meniscus and in older athletes arthritis is more likely to be a possible cause.

Rest is important. Avoid any activities which aggravate or make the condition worse. Change training methods if possible, for example substitute swimming, cycling or the cross trainer machine for running. It is possible the symptoms may simply disappear by themselves. In children the condition may just suddenly clear up, however, if it doesn’t then surgery is an option, although they do stand a chance of the cyst returning.

Try wearing a compression wraparound knee support to help reduce the swelling. If symptoms do not clear up on their own, seek professional advice and have a full knee examination to identify the cause of the cyst or swelling.

What can a physiotherapist do?
They will examine the knee and diagnose what is causing the swelling in the first place. In more serious cases a surgeon may operate to correct whatever is causing the swelling, including cartilage meniscus, foreign bodies or bursa that may need removing. The patient is likely to be out of action for eight to 12 weeks following surgery.

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