Baker cysts are small, fluid-filled lumps that form on the back of your knee. They grow after something damages your knee joint or causes swelling around it. They usually aren’t serious, but you should still see a healthcare provider to get it diagnosed. Baker cysts can share symptoms with more serious issues like blood clots.
A Baker cyst is a small, fluid-filled bump that forms on the back of your knee. Healthcare providers sometimes call Baker cysts popliteal cysts and synovial cysts. These are all different names for the same issue.
Baker cysts develop when something damages your knee joint or the tissues around it and extra fluid drains out of your knee. The fluid can only drain in one direction — out the back of your joint. That buildup forms the sac that becomes a Baker cyst.
Baker cysts are benign growths. That means they aren’t tumors and are never a symptom of (and don’t cause) cancer.
Visit a healthcare provider as soon as you notice a new growth or lump behind your knee, especially if you recently injured your knee or have arthritis.
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The most obvious symptom of a Baker cyst is the bump that forms behind your knee. Other common Baker cyst symptoms include:
Some people with a Baker cyst don’t experience symptoms. You might not know you have one until a healthcare provider notices while they’re diagnosing other issues or conditions that affect your knee.
Baker cysts can sometimes cause swelling and discoloration in your lower leg that can be similar to the symptoms of a blood clot. A blood clot is an emergency. Visit a healthcare provider right away if you think you might have a blood clot. Your provider can check out your symptoms and determine if it’s a Baker cyst or a blood clot.
Anything that damages your knee joint can cause swelling and trigger a Baker cyst. The most common causes are different types of knee arthritis and injuries.
The most common forms of arthritis that cause Baker cysts include:
If you experience a knee injury, the damage can cause swelling in your knee that leads to a Baker cyst. Knee injuries that cause Baker cysts include:
Injuries that damage your knee ligaments can cause Baker cysts, including:
Anyone can develop a Baker cyst, especially if you have arthritis or experience an injury. Some groups of people are more likely to have a Baker cyst, including:
The most common complication of a Baker cyst is rupturing (breaking). A ruptured Baker cyst happens when the sac around the cyst fills up with fluid too fast or with too much pressure and bursts. If you’ve ever accidentally filled up a water balloon too quickly, you know what can happen if fluid flows into a thin, rubbery container with too much pressure — it pops.
A ruptured Baker cyst can cause other symptoms in your knee and lower leg, including:
A healthcare provider will diagnose a Baker cyst with a physical exam. They’ll examine your leg and look for a lump on the back of your knee. Tell your provider when you first noticed the bump and if you’re experiencing any other symptoms. If you hurt your knee, tell your provider what you were doing before the injury.
Your provider might use a few imaging tests to diagnose a Baker cyst, including:
Usually, your healthcare provider will treat the cause of a Baker cyst rather than the cyst itself. The cyst will usually go away when the damage in your knee that caused it has healed. Which treatments you’ll need depends on which injury or condition you have.
Most minor injuries can be treated with the RICE method:
Your healthcare provider might suggest medications to relieve pain and reduce swelling.
Most people can take over-the-counter (OTC) NSAIDs (ibuprofen, aspirin and naproxen) or acetaminophen (Tylenol®). Don’t take these medications for more than 10 days in a row without talking to your provider.
Your provider might suggest prescription corticosteroids or cortisone shots.
Your provider might suggest physical therapy if you’re recovering from an injury or have arthritis. A physical therapist will show you stretches and exercises that strengthen the muscles around your affected knee.
You might need knee surgery to repair torn cartilage or ligaments in your knee, or if you fractured a bone.
It’s rare, but you may need surgery to drain or remove a Baker cyst if it’s causing severe pain or making it hard to use your knee.
Your surgeon will tell you which type of surgery you’ll need and what to expect while you’re recovering.
The best way to prevent a Baker cyst is to prevent knee injuries. During sports or other physical activities:
Follow these general safety tips to reduce your risk of an injury:
How long a Baker cyst lasts depends on what caused it. Most Baker cysts go away as soon the swelling goes down and your knee starts to heal, usually within a few weeks.
It’s possible for a Baker cyst to go away on its own. But you should always visit a healthcare provider as soon as you notice any new lumps or growths on your body. Even if you don’t need treatment, a provider needs to diagnose a Baker cyst and make sure it’s not something more serious.
As your knee heals, the fluid in the cyst is absorbed back into your body. Follow your provider’s suggestions to help your knee heal and to prevent any more damage.
Visit a healthcare provider as soon as you notice a lump on your leg. It’s important to get it diagnosed — a healthcare provider will determine if it’s a Baker cyst or something more serious (like a blood clot).
Go to the emergency room if you’ve experienced trauma, think you have a broken bone or think your knee is dislocated. Never try to force a joint back into place on your own. Keep your knee as still as possible and go to the emergency room.
You should be able to sleep normally with a Baker cyst, even if you sleep on your back. It’s unlikely the pressure from lying down will rupture the cyst. Talk to your healthcare provider if putting pressure on the back of your knee on or near the cyst hurts or is uncomfortable.
A note from Cleveland Clinic
A Baker cyst is a fluid-filled lump that grows on the back of your knee. It usually forms after an injury or if something causes swelling inside your knee joint.
Most Baker cysts aren’t serious, but you should always have a healthcare provider examine and diagnose any new bumps or growths on your body. A Baker cyst can sometimes go away on its own and it doesn’t always cause pain. However, it’s important to have the condition diagnosed by your healthcare provider to make sure it’s not a sign of a more serious condition
Last reviewed by a Cleveland Clinic medical professional on 06/06/2023.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy