Facet synovial cyst
In plain language
A fluid-filled sac arising near a spinal facet joint that may crowd a nerve or the spinal canal.
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3 things to know first
- It is usually a joint-related fluid sac. It is not automatically a tumor.
- Many cause no symptoms. Size and position determine whether a nerve is affected.
- The associated joint matters. Degenerative facet changes often accompany it.
What it is
Facet joints connect the back parts of adjacent vertebrae. A synovial cyst is a sac near one of these joints containing joint-like fluid. It is most often discussed in the lower back, where it may extend into the spinal canal or a nerve passage.
Why it appears on your report
MRI can show the cyst and its relationship to nerves; CT may help show nearby bone changes. The report may describe the level, side, size, and whether a nerve root or thecal sac is compressed.
How serious is it
An incidental small cyst may simply be observed. A cyst associated with leg pain, numbness, or weakness deserves clinical assessment. Imaging alone cannot prove that it causes all symptoms.
When to seek care urgently
Seek urgent care for progressive leg weakness, new saddle numbness, or bladder or bowel dysfunction.
What usually happens next
- Match the cyst level and side with symptoms.
- Review nerve compression and other spine findings.
- Discuss monitoring or specialist treatment if symptoms persist.
Further reading
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