A Baker’s cyst, or popliteal cyst, is a fluid filled lump or swelling behind the knee. It is usually caused by excess fluid that comes from the knee joint.
Baker’s cyst symptoms
If the cyst is small, you might not notice it.
Otherwise, you may have aching, a swelling or lump behind your knee, or feel pressure when you straighten your leg.
Your doctor can often diagnose a Baker’s cyst by examining your knee and shining a torch through the lump.
You might also have an ultrasound or MRI scan.
Baker’s cyst complications
Occasionally Baker’s cysts become infected, grow bigger or can bleed.
Sometimes a Baker’s cyst ruptures or bursts, causing pain and swelling in your calf. Your doctor may want to rule out a serious problem such as a blood clot (deep vein thrombosis).
Baker’s cyst treatments
If a child has a painless Baker’s cyst, it can usually be left alone. In children, most Baker’s cysts disappear eventually without treatment.
Taking supplements or wearing a brace is unlikely to help with your symptoms.
If you have a troublesome Baker's cyst, your doctor may drain it using an ultrasound and inject it with corticosteroids, which has been shown to result in significant improvements and a low chance of the cyst coming back.
If the cyst is associated with arthritis or a knee injury, then treating these conditions can help.
For some people, surgery is needed to fix the cause. For example, repairing a torn cartilage might help. Removing the cyst alone isn't helpful, as it usually recurs unless the underlying cause is addressed.
Your doctor can advise you on the treatment options that are best for you.
Last reviewed: July 2017