Baker Cyst (Popliteal Cyst)

A Baker’s cyst is a small, fluid-filled bump that forms on the back of your knee. Healthcare providers sometimes call them Baker cysts or popliteal cysts.

They develop when something damages your knee joint or the tissues around it. The damage makes extra fluid drain 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’s cyst.

Popliteal cysts are benign growths. That means they aren’t tumors and are never a sign or symptom of cancer. But visit a healthcare provider as soon as you notice a new growth or lump behind your knee.

Baker’s cyst symptoms

The bump that forms behind your knee is the most obvious symptom of a Baker cyst. You might also notice:

• Knee pain
• Stiffness
• Trouble bending your knee as far as you usually can
• Swelling in your knee, thigh or calf

You might not experience any symptoms. You may never know you have a popliteal cyst until a healthcare provider notices it during a physical exam.

Baker’s cyst causes

Anything that damages your knee joint can cause swelling and lead to a popliteal cyst. The most common causes are knee arthritis and injuries.

Arthritis damages tissue in your joints over time. That breakdown can make your body produce extra fluid. Then, the fluid can build up in your knee and become a Baker’s cyst.

Injuries can also lead to Baker’s cysts. The damage from an injury can cause swelling in your knee. That can also lead to fluid buildup which can turn into a cyst.

Baker’s cyst risk factors

Anyone can develop a Baker’s cyst. But some people may be more likely to, including:

• Adults between the ages of 35 and 70
• Athletes
• People who put lots of pressure on their knees at work or for a physical hobby
• People with arthritis

Complications of cysts behind your knee

A cyst can rupture if it fills up too fast or with too much pressure. Picture filling up a water balloon too fast. Too much water or pressure makes the balloon burst. The same thing can happen to a cyst.

A ruptured 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 the feeling comes from inside your body
• Nerve damage
• Compartment syndrome

Baker’s cysts can sometimes cause swelling and discoloration in your lower leg. These can be similar to symptoms of a blood clot. A blood clot is an emergency. See a healthcare provider right away if you think you might have one.

How doctors diagnose popliteal cysts

A healthcare provider will diagnose a Baker’s cyst with a physical exam. They’ll examine your leg and look for a lump. 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 happened.

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

• X-ray
• Ultrasound
• MRI

Baker’s cyst treatment

Your healthcare provider will treat the cause of the Baker’s cyst. The cyst will usually go away when the damage in your knee that led to it heals. You might need:

• The RICE or MEAT methods: These are ways of managing injuries at home. Your provider will suggest the one that’s best for you and your knee joint.
• Medications: You might need over-the-counter (OTC) anti-inflammation medications like NSAIDs or acetaminophen. Your provider might give you a prescription for corticosteroids or a cortisone shot.
• Physical therapy: Your provider might suggest physical therapy if you’re recovering from an injury or have arthritis. A physical therapist will give you exercises that strengthen the muscles around your affected knee.
• Surgery: You may need surgery if you have a severe knee injury, like a ligament tear or broken bone. It’s very rare to need surgery to remove a Baker’s cyst. Your provider will usually only suggest it if the cyst causes severe pain. Or makes it hard to use your knee.

When should I see my healthcare provider?

Some popliteal cysts go away on their own. But don’t assume anything about a new lump or growth. Visit a healthcare provider. They’ll diagnose a cyst and make sure it’s not something more serious.

How long does a Baker’s cyst last?

It depends on what caused it. Most cysts go away as soon as the swelling gets better. This is usually within a few weeks. Even if you have arthritis, a cyst won’t be permanent.

Your body will reabsorb the fluid as your knee heals. Follow your provider’s suggestions to prevent any more damage.