Synovial cysts are fluid-filled sacs that form in the joints of the spine, most commonly in the lumbar (low-back) region, due to age-related bone degeneration. These cysts may cause cramping, tingling, or pain in the lower back or leg, or no symptoms at all.
Treatment may include injections, medicines, and, rarely, surgery.
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Synovial cysts are fluid-filled sacs that occur in the spine. They can form in the cervical (neck), thoracic (upper back), or lumbar (lower back) areas, but most develop in the lumbar spine.
This type of cyst results from age-related degeneration of the facet joints of the vertebrae (spinal bones). They are always benign (noncancerous).
Most synovial cysts are asymptomatic, meaning they do not cause symptoms. Asymptomatic synovial cysts often went undiagnosed until the last decade, when improvements in imaging began revealing more of them.
The facet joints of the spine are small connector bones that link two vertebrae together and allow you to bend and twist your upper body. They also limit over-rotation and keep the vertebrae from slipping out of place.
Facet joints are made up of cartilage, a fibrous capsule of connective tissue and ligaments, and synovial fluid, which lubricates the joints and decreases friction. As spinal facet joints break down, they can produce more fluid to protect the joint than a healthy joint needs. This extra fluid can build up in the synovial lining of the joint, causing a cyst to form.
The fluid in the cyst is not dangerous on its own. It is not under any pressure within the joint and will not cause problems unless it pushes on the spine. Even the largest spinal synovial cysts rarely cause problems.
Since most synovial cysts do not cause symptoms and are benign, they do not have to be removed. They may be treated with nonsurgical approaches first if they cause mild symptoms. Surgery is only performed when nonsurgical approaches fail to relieve symptoms.
The risk factors for synovial cysts include:
Although these cysts are uncommon and don’t often produce symptoms, they may cause issues with your spine.
Spinal stenosis, or the narrowing of the spinal column, is one of these issues. As the open spaces within the spinal column compress, pressure can increase on the spinal cord and nerves, causing pain and cramping in the back or legs. Standing may worsen the symptoms.
Very rarely, synovial cysts can cause cauda equina syndrome (CES) to develop — a serious condition that may require emergency medical attention. CES is when there is a bundle of spinal nerves and nerve roots in the lumbar or sacral (tailbone) area. Its name means “horse tail” in Latin because the bundle of nerves resembles a horse’s tail.
Although you cannot prevent a synovial cyst, you can lower your risk by taking care of your spine.
For example:
Synovial cysts are uncommon. According to the National Institutes of Health, their incidence is thought to be less than 0.5% of the general population with symptoms.
Synovial cysts usually cause no symptoms until they become large enough to put pressure on the spinal cord or nerves within the spinal column. When they have grown to that point, spinal stenosis, or narrowing of the spinal column, often results, and you may begin to have symptoms.
Synovial cyst symptoms might include:
If you experience symptoms of a synovial cyst that make it hard to complete your activities of daily living, talk to your doctor.
Synovial cysts can best be seen with imaging. Specifically, an MRI enables your doctor to see inside the spinal column to find cysts or any other issues that may be causing your symptoms.
If an MRI reveals a cyst, your doctor may order additional tests, such as x-rays or ultrasound, to check for spine and spinal column damage. A surgeon may also use these images to look for instability issues before cyst-removal surgery.
Your doctor may recommend nonsurgical treatment options for your synovial cyst.
If certain activities make your symptoms worse, such as exercising or standing at work, your health care provider can help you find ways to modify your activities to lessen symptoms. Easy stretching and heat or cold therapy may reduce discomfort, but ask your doctor first.
There are two types of injections used to treat a synovial cyst:
Over-the-counter (OTC) pain relievers like acetaminophen and ibuprofen can reduce synovial cyst pain. If they do not help, your doctor may prescribe a stronger pain medication.
If your cyst does not cause your problems, your provider may recommend not treating it. They may recommend a watch-and-wait approach to see if the cyst grows.
If nonsurgical synovial cyst treatments do not provide relief, your provider might recommend surgery to remove the cyst. This surgery is not difficult but requires recovery time. Your doctor may be able to use a minimally invasive surgical procedure to remove the cyst, which may lessen your pain and recuperation time.
By UPMC Editorial Staff. Last reviewed on 2025-06-26.
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