Synovial Cyst

A synovial cyst is a fluid-filled sac that forms between joints in your spine. They’re most common in your lumbar spine in your lower back.

Synovial cysts form when fluid builds up inside the synovial membrane in a joint. The membrane swells up and balloons out of its usual place. The cyst can stick out from between the bones in your joint. Cysts are almost never cancerous.

Symptoms of a synovial cyst

You might have a spinal synovial cyst and never know it. Many don’t cause symptoms. If you do experience symptoms, you might feel:

• Back pain
• Pain in your legs or butt
• Muscle weakness in your legs
• Tingling or numbness in your legs, groin or butt

Pain from a synovial cyst is often referred. That means you’ll feel pain or other symptoms in another part of your body. That’s why you might have symptoms in your butt or legs. A cyst in your spine can press on nerves and cause symptoms lower in your body, where those nerves travel.

You might notice the symptoms change depending on what you’re doing. It may feel better to stand up or move. Or symptoms may get better when you sit or lie down.

Synovial cyst causes

Small facet joints hold all the bones in your spine together. Facet joints rest on each other to keep two spine bones connected. A synovial membrane cushions the space between them.

Spinal synovial cysts form when facet joints wear down. Your body might make extra synovial fluid in response. The excess fluid fills up the membrane like a tiny water balloon.

Causes of synovial cysts can include:

• Natural aging: Normal wear and tear is the most common cause of synovial cysts. Your joints naturally break down over time as you age. Your facet joints are no different. Over time, the disks and other cushioning in your joints break down. This can lead to cysts.
• Spine arthritis: Arthritis in your facet joints can cause inflammation that damages them. Your body may produce extra synovial fluid in response to changes in your spine’s stability. That can lead to a cyst forming.
• Spine injuries: Any trauma that damages your spine can make your facet joints break down. This is much less common than age-related damage.

Risk factors

Synovial cysts almost always develop in people over 50. That’s because they usually happen after natural aging wears down your facet joints.

Complications of this condition

Synovial cysts can cause spinal stenosis. This can make symptoms like pain and numbness worse. It can also make it hard to walk and move.

Severe cases can press on nerves that help you control your bladder and bowel. This can make you lose control of your pee or poop. But this is very rare.

How doctors diagnose this condition

A healthcare provider will diagnose a synovial cyst with a physical exam and imaging tests. They’ll examine your back and ask about the symptoms you’re feeling. Tell your provider when the symptoms started. Let them know if any positions or movements make symptoms better or worse.

Your provider will use imaging tests to take pictures of your spine. You might need:

• Spine X-ray
• MRI
• CT scan

Synovial cyst treatment options

You may not need treatment for a synovial cyst. Especially if it’s not causing symptoms. Your healthcare provider might suggest keeping an eye on it with follow-up appointments and imaging tests. If you need them, treatments can include:

• Pain medications: You might be able to manage symptoms with over-the-counter NSAIDs or acetaminophen. These relieve pain and reduce inflammation. Your provider might give you prescription-strength medications if you have more severe pain.
• Physical therapy: Strengthening your back muscles can help take pressure off your spine. A physical therapist will give you exercises and stretches to help.
• Spine injections: Your provider might inject medication into your spine to relieve symptoms. You might need a corticosteroid to treat inflammation. You may need a nerve block to numb nerves near the cyst.
• Aspiration: This is using a needle to remove fluid from the facet cyst. Your provider will safely insert a needle into your back. They’ll remove some synovial fluid. This can make the symptoms better right away. But there’s a chance the cyst will reform.
• Rupturing the cyst: If your provider can’t aspirate a cyst, they may rupture it. Instead of removing fluid with a needle, they’ll safely fill it with sterile fluid until it bursts. The fluid will harmlessly leak into your spinal cord. This will also improve symptoms immediately.
• Surgery: Your provider will suggest surgery if a synovial cyst causes severe pain or weakness. Or if other treatments don’t work. Your surgeon will remove the cyst. They might also do a spinal fusion. This can strengthen your spine near where the cyst formed. This will prevent cysts from forming in those joints again.

When should I see my healthcare provider?

Visit a healthcare provider if you have back pain that lasts for more than a week. See a provider right away if you lose feeling in any part of your body, or feel weakness in your arms or legs that gets worse quickly. Especially if you lose your ability to control functions like peeing or moving.

What can I expect if I have a synovial cyst?

A synovial cyst is usually treatable. But you should expect to try a few different treatments. Your provider will help you find the right ones. And they’ll tell you when it’s time to think about removing the cyst.

There’s always a chance a cyst will grow back. Even if you have it removed. Tell your provider if you notice symptoms coming back or getting worse.

Are synovial cysts the same thing as ganglion cysts?

Synovial cysts and ganglion cysts are the same kind of cyst. But they usually grow in different places. Ganglion cysts usually form on your hands, wrists or feet. Synovial cysts almost always happen between facet joints in your neck or lower back.

Technically, a ganglion cyst is a type of synovial cyst. It’s a growth full of synovial fluid. But healthcare providers use the catch-all term synovial cyst to refer to the kind that grows in your spine.

Visit a healthcare provider if you have a new or changing growth anywhere on your body. No matter what they end up calling it.