Baker's Cyst

What is a Baker cyst?

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.

What are Baker cyst symptoms?

The most obvious symptom of a Baker cyst is the bump that forms behind your knee. Other common Baker cyst symptoms include:

• Knee pain.
• Stiffness.
• Trouble bending your knee as far as you usually can (a limited range of motion).
• Swelling in your knee or on your leg around it.

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.

What causes Baker cysts?

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:

• Osteoarthritis.
• Rheumatoid arthritis.
• Gout.

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:

• Repetitive strain injuries (overuse injuries).
• Meniscus tears.
• Hyperextensions.
• Sprains.
• Dislocations.
• Bone fractures.

Injuries that damage your knee ligaments can cause Baker cysts, including:

• ACL tears.
• MCL tears.
• LCL tears.
• PCL tears.

Baker cyst risk factors

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:

• People 35 to 70 years old.
• Athletes.
• People who put lots of pressure on their knees at work or during a hobby.
• People with arthritis.

What are Baker cyst complications?

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:

• Sharp, stabbing pain in your knee or calf.
• Swelling in your calf and lower leg.
• A feeling like water is running down your leg (but inside your body).
• Nerve damage.
• Compartment syndrome (painful extra pressure in your muscles).

How are Baker cysts diagnosed?

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.

What tests do healthcare providers use to diagnose a Baker cyst?

Your provider might use a few imaging tests to diagnose a Baker cyst, including:

• X-rays.
• Ultrasound.
• Magnetic resonance imaging (MRI).

How are Baker cysts treated?

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.

RICE method

Most minor injuries can be treated with the RICE method:

• Rest: Stop the physical activity that caused the injury to avoid making it worse.
• Ice: Apply an ice pack or cold compress for 10 to 15 minutes every hour for the first day after your injury. After one day, you can apply ice every three to four hours. Don’t apply ice directly to your skin (wrap the ice pack in a towel or washcloth).
• Compression: Compression helps reduce blood flow to your injured knee and reduces swelling. Apply a compression bandage or wrap around your knee. You can also wear compression pants to help keep pressure on your knee.
• Elevation: If possible, lift your knee and lower leg above the level of your heart. Support your leg with pillows, blankets or cushions.

Medications

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.

Physical therapy

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.

Knee surgery

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.

How long does a Baker cyst last?

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.

What happens if you leave a Baker cyst untreated?

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.

Can you prevent a Baker cyst?

The best way to prevent a Baker cyst is to prevent knee injuries. During sports or other physical activities:

• Wear the right protective equipment.
• Don’t “play through the pain” if your knee hurts during or after physical activity.
• Give your body time to rest and recover after intense activity.
• Stretch and warm up before playing sports or working out.
• Cool down and stretch after physical activity.

Follow these general safety tips to reduce your risk of an injury:

• Make sure your home and workspace are free from clutter that could trip you or others.
• Always use the proper tools or equipment at home to reach things. Never stand on chairs, tables or countertops.
• Use a cane or walker if you have difficulty walking or have an increased risk of falls.

When should I see my healthcare provider?

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).

When should I go to the ER?

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.

What questions should I ask my healthcare provider?

• Do I have a Baker cyst or another issue?
• What caused the cyst?
• Which treatments will I need?
• Will I need surgery?
• How long will the Baker cyst last?

How do I sleep with a Baker cyst?

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.