What is a synovial cyst of the spine?

A synovial cyst of the spine is a fluid-filled sac that develops along the spine. It’s the result of degeneration of a facet joint of the vertebrae of the spine. Most synovial cysts develop in the portion of the lower spine called the lumbar spine.

These cysts are uncommon and often don’t produce symptoms. The cysts aren’t deadly or cancerous. However, they may cause issues with your spine like spinal stenosis.

Spinal stenosis is narrowing or shrinking of the spinal column. Pressure can increase on the spinal cord and the nerves inside the column as the open space inside the spinal column decreases. Symptoms increase as pressure increases. Symptoms of spinal stenosis include pain and cramping in the back and legs. The discomfort is often worse if you stand for a long time.

How does a synovial cyst develop?

As a facet joint in your spine breaks down it can produce more fluid than a healthy joint. The fluid is useful for the damaged joint. It provides extra lubrication and helps ease the joint’s movements. However, a cyst may develop in response to the extra fluid. As the fluid builds up it can get caught in the synovial lining of the joint. Eventually a cyst may form.

The fluid in the cyst is not dangerous. It’s not under any pressure and won’t cause any problems until it begins pushing on the spine. Even very large cysts are rarely a problem.

What are the risk factors for a synovial cyst?

Synovial cysts are most common in older adults since they are the result of deterioration of the spine. It’s rare that someone under 50 years of age will develop a synovial cyst.

What are the symptoms of a synovial cyst?

A synovial cyst rarely causes noticeable or detectable symptoms until it becomes large enough to interfere with the spine. At that point the cyst may start to cause symptoms of spinal stenosis.

Symptoms might include:

  • pain in the lower back
  • pain in one or both legs
  • pain that radiates down the back of the leg and to the feet
  • painful cramping in the legs
  • numbness or tingling in one or both legs
  • increased pain and symptoms when standing that relieves or eases when sitting

How are synovial cysts diagnosed?

A synovial cyst is best seen with an MRI. This scan allows your doctor to see inside the spinal column and find any cysts or anything else causing your symptoms. Other imaging tests like an X-ray or ultrasound may also be able to detect the cyst.

If your doctor finds a cyst, they may want to conduct additional scans to check the spine and spinal column for damage. It’s important for your doctor to assess if there is any damage to the spine. Also, your doctor will want to look for any instability issues before performing surgery to remove the cyst.

How are synovial cysts treated?

Nonsurgical treatment options for a synovial cyst include:

Pain medications

Mild over-the-counter (OTC) pain medications like acetaminophen and ibuprofen can reduce pain caused by a cyst. Your doctor may prescribe a stronger medication if OTC treatments don’t help.

Observation

Your doctor may suggest leaving the cyst alone if it isn’t causing any problems. The cyst might not grow large enough to cause symptoms. If it does, you can revisit treatment options.

Activity modification

If you experience symptoms only with certain activities, like exercising or your job, your doctor can help you find ways to modify your activities and movements to reduce symptoms.

Mild stretching and exercise may also help. But it’s important to get your doctor’s approval first. And heat and cold therapy can reduce discomfort and pain.

Injections

Two types of injections are used to treat synovial cysts. A facet injection can drain the fluid from the cyst through the facet joint. A steroid is inserted after the fluid is removed to help reduce swelling and inflammation.

Another type of injection, an epidural steroid injection, may be used to treat pain caused by a synovial cyst. This common treatment doesn’t reduce or remove the cyst. Instead, the injection aims to reduce the pain caused by the cyst. However, pain relief is temporary, and you may need additional treatments to maintain the effect.

If these nonsurgical treatments don’t work or aren’t an option for you, your doctor may recommend surgery to remove the cyst. The surgery isn’t very difficult, but you will need time to recuperate. Newer surgical techniques have limited the size of the incision you doctor needs to make to remove the cyst. That cuts down on pain and recovery time.

Is a synovial cyst ever dangerous?

Synovial cysts are rarely dangerous. In some cases, a condition called cauda equina syndrome (CES) may develop because of a synovial cyst. This syndrome is a serious condition and requires emergency medical attention.

CES affects the cauda equina (nerve roots) in the lumbar spine. You may lose sensation and the ability to move when these nerve roots become compressed. This condition may also affect other nerves, like those connected to the bowels and bladder.

The damage may be permanent if this condition isn’t treated quickly. Recovering full function may be difficult.

What’s the difference between ganglion and synovial cysts?

A ganglion cyst is a fluid-filled sac that often develops in the wrists and ankles. And doctors can rarely tell the difference between ganglion and synovial cysts with a naked eye. It’s only after your doctor removes and inspects the cyst that they can tell the difference.

A synovial cyst has a thin film of tissue around the cyst (synovium). A ganglion cyst doesn’t have this tissue. But your doctor won’t need to distinguish between them since both are treated the same way.

Takeaway

Synovial cysts of the spine aren’t deadly or cancerous and often don’t produce symptoms. Symptoms that may occur include back pain or numbness, tingling, or cramping in the legs. There are treatments to help reduce discomfort, such as medication, activity modification, and injections.

In rare cases, cauda equina syndrome (CES) may develop because of a synovial cyst. This syndrome is a serious condition and requires emergency medical attention.