Baker’s cyst

The cyst behind the knee is filled with the lubricating fluid known as synovial fluid and is in the wrong place; this liquid is usually found inside the knee joint. This type of cyst is usually the result of an underlying condition with the knee joint, such as osteoarthritis or even a cartilage tear. The conditions can cause the knee to produce too much fluid.

Our knee experts can help to diagnose and treat a range of cysts, including a Baker’s cyst. The cyst can be sometimes be diagnosed during a physical exam with your knee consultant. However, a Baker's cyst may present in a similar way to a blood clot. Sometimes imaging tests may be required to get an accurate diagnosis.

Treatment options vary. If the cyst is large and reducing mobility, the consultant may organise the draining of the cyst using a needle, often performed using an ultrasound, termed needle aspiration.  

Sometimes, keyhole or arthroscopic surgery may be arranged to repair the source of the issue - if it is a cartilage tear causing fluid to collect behind in the knee, your consultant may discuss repairing the torn cartilage at the same time as draining the cyst.