Synovial Facet Cyst

A synovial facet cyst is a small, fluid-filled sac that forms in the facet joint of the spine—most often in the lower back (lumbar region). These cysts develop due to degenerative changes in the spine and may compress nearby nerves, causing lower back pain and radiating leg pain (sciatica).
While some facet cysts cause no symptoms, others can lead to spinal canal narrowing (stenosis) and significant discomfort.

How Common It Is and Who Gets It? (Epidemiology)

Synovial facet cysts are uncommon but typically occur in older adults (over 50 years) due to arthritis and wear-and-tear changes in the spine. They are most frequently found at the L4–L5 level, where motion and degeneration are greatest. Both men and women are equally affected.

MRI axial section showing the facet joint.

Why It Happens – Causes (Etiology and Pathophysiology)

Facet joints connect the vertebrae at the back of the spine and allow for smooth movement. They are surrounded by a capsule that produces synovial fluid—a lubricant that helps the joints move easily.
With aging and degeneration:

• Intervertebral discs lose height, putting more stress on facet joints.

• Facet arthritis develops, leading to inflammation and joint instability.

• The capsule may produce excess synovial fluid, which can form a pocket or cyst.
  This cyst may press on nearby nerve roots or the spinal canal, causing pain and neurological symptoms.
  Occasionally, bleeding into the cyst (facet cyst hematoma) causes rapid symptom worsening.

How the Body Part Normally Works? (Relevant Anatomy)

The facet joints are located behind each vertebra and guide motion in the spine. Each joint has smooth cartilage and is enclosed by a capsule filled with synovial fluid for lubrication.
When degeneration occurs, the capsule may weaken, bulge, and form a cyst. This cyst can intrude into the spinal canal, reducing the space available for nerves.

What You Might Feel – Symptoms (Clinical Presentation)

Symptoms depend on the cyst’s size and location:

• Lower back pain—often worse with standing or walking.

• Leg pain (sciatica): Radiating pain from the lower back into one or both legs.

• Numbness or tingling in the legs or feet.

• Weakness in the legs if the cyst compresses nerve roots.

• Neurogenic claudication: Pain in the buttocks and legs that worsens with walking and improves when sitting or bending forward.

• Sudden worsening of pain if bleeding occurs inside the cyst.

Symptoms are often similar to spinal stenosis or a herniated disc.

How Doctors Find the Problem? (Diagnosis and Imaging)

Diagnosis begins with a physical exam and neurological assessment.

• MRI: The gold standard imaging test for detecting facet cysts and evaluating nerve compression.

• CT scan: May be used for detailed bone structure evaluation or to guide injections.

• X-rays: Can show degenerative changes or joint instability.
  A facet cyst appears on MRI as a fluid-filled mass near a degenerated facet joint.

Classification

Synovial facet cysts are classified by their location and associated findings:

• Lumbar cysts: Most common (especially L4–L5).

• Cervical or thoracic cysts: Rare.

• With or without nerve compression: Symptomatic (compressive) or asymptomatic (non-compressive).

Other Problems That Can Feel Similar (Differential Diagnosis)

Conditions that may mimic facet cyst symptoms include:

• Lumbar disc herniation

• Spinal stenosis

• Degenerative spondylolisthesis

• Epidural hematoma or abscess

• Tumors of the spine

Treatment Options

Non-Surgical Care

Most patients start with conservative management:

• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce pain and inflammation.

• Physical therapy: Strengthening and flexibility exercises improve stability and relieve pressure.

• Heat or cold therapy: Helps reduce stiffness and discomfort.

• Epidural steroid injections: Can temporarily reduce inflammation and pain.

• CT-guided cyst rupture with steroid injection: Involves breaking the cyst and injecting anti-inflammatory medication to relieve nerve compression. Some patients may need repeat injections.

Surgical Care

Surgery is considered when symptoms persist despite conservative treatment or neurological deficits develop.
Surgical options include:

• Laminectomy and decompression: Removes part of the bone and facet joint to relieve nerve pressure and remove the cyst. Usually done for one-sided (unilateral) symptoms.

• Facetectomy with fusion: Involves removing part or all of the facet joint and stabilizing the spine with screws and rods. Indicated for:

  • Bilateral or recurrent cysts

  • Central spinal canal stenosis

  • Instability of the vertebrae

Minimally invasive techniques allow smaller incisions, faster recovery, and less tissue disruption.

Recovery and What to Expect After Treatment

• Conservative management: Improvement may occur over several weeks or months.

• After surgery: Most patients experience immediate relief of leg pain. Hospital stays are typically 1–2 days for minimally invasive surgery.

• Rehabilitation: Physical therapy begins soon after surgery to restore movement and strengthen the back.
  Full recovery usually occurs within 4–8 weeks.

Possible Risks or Side Effects (Complications)

Potential risks include:

• Recurrence of the cyst

• Nerve injury or persistent pain

• Infection or bleeding

• Spinal instability (may require fusion)

• Cerebrospinal fluid (CSF) leak

Long-Term Outlook (Prognosis)

The long-term outlook is excellent. Most patients achieve lasting pain relief and improved mobility after treatment. The recurrence rate after surgery is very low, especially when spinal stabilization is performed. Early diagnosis and treatment prevent chronic nerve compression.

Out-of-Pocket Costs

Medicare

CPT Code 63047 – Decompression / Laminectomy with Cyst Excision: $271.76
CPT Code 63005 – Limited Facet Cyst Excision: $300.40
CPT Code 22612 – Fusion (if needed): $382.85
CPT Code 22842 – Instrumentation (Rods, Screws, Plates – 3–6 Segments): $185.26

Under Medicare, 80% of the approved costs for these spine procedures are covered once your annual deductible has been met. Patients are responsible for the remaining 20%. Supplemental insurance plans—such as Medigap, AARP, or Blue Cross Blue Shield—usually pay this 20% portion, meaning most patients have little to no out-of-pocket costs for Medicare-approved surgeries. These supplemental policies work directly with Medicare to ensure comprehensive coverage for spinal decompression and stabilization procedures like laminectomy, cyst excision, and fusion.

If you have secondary insurance—such as Employer-Based coverage, TRICARE, or Veterans Health Administration (VHA)—it serves as a secondary payer once Medicare has processed the claim. After your deductible is met, the secondary plan may cover remaining coinsurance or additional costs. Secondary insurance plans typically have a modest deductible, ranging from $100 to $300 depending on the specific policy and network coverage.

Workers’ Compensation
If your lumbar facet cyst or spinal compression resulted from a workplace injury, Workers’ Compensation will cover the full cost of surgical treatment, including decompression, cyst excision, and spinal fusion if necessary. You will have no out-of-pocket expenses under an accepted Workers’ Compensation claim.

No-Fault Insurance
If your spinal condition or facet cyst was caused or worsened by a motor vehicle accident, No-Fault Insurance will pay for all related surgical and hospital expenses, including decompression, cyst excision, and fusion procedures. The only possible cost to you may be a small deductible depending on your policy’s terms.

Example
Patricia, a 62-year-old patient with lumbar spinal stenosis and a facet joint cyst, underwent decompression with cyst excision (CPT 63047) and posterior fusion with instrumentation (CPT 22612 + 22842) to stabilize her spine. Her Medicare out-of-pocket costs were $271.76, $382.85, and $185.26, respectively. Since she had supplemental coverage through AARP Medigap, the 20% that Medicare did not pay was fully covered, leaving her with no out-of-pocket expense for her surgery.

Frequently Asked Questions (FAQ)

Q. What causes a synovial facet cyst?
A. It develops from degenerative arthritis in the facet joints, which produces excess synovial fluid that collects and forms a cyst.

Q. How is a synovial facet cyst different from a herniated disc?
A. Both can compress nerves and cause sciatica, but a facet cyst arises from a joint, while a herniated disc comes from the intervertebral disc.

Q. Can facet cysts go away on their own?
A. Small cysts sometimes shrink or rupture naturally, but most persist or enlarge over time.

Q. When is surgery necessary?
A. Surgery is recommended for persistent pain, neurological symptoms, or spinal instability after conservative treatment fails.

Summary and Takeaway

A synovial facet cyst is a fluid-filled sac that forms due to arthritis and degeneration in the spine’s facet joints. While many cases improve with medications, therapy, or injections, surgery provides lasting relief for persistent or severe symptoms. Modern minimally invasive techniques make surgical removal safe, effective, and associated with rapid recovery.

Clinical Insight & Recent Findings

A recent case report described a 64-year-old woman with lumbar synovial facet cyst at the L4–L5 level presenting with neurogenic claudication and radicular pain after prior hip arthroplasty. MRI revealed an extradural cyst compressing the right L5 nerve root and narrowing the spinal canal.

The patient underwent posterior laminectomy, partial arthrectomy, cyst excision, and instrumented posterolateral fusion, which led to significant improvement in walking ability and only mild residual back pain two years post-surgery. The authors emphasized that lumbar facet synovial cysts, most commonly found at L4–L5 due to high mobility and facet degeneration, can mimic hip or spinal stenosis symptoms, complicating diagnosis. MRI remains the gold standard, showing well-defined, smooth, extradural lesions adjacent to facet joints.

While conservative management with analgesics, corticosteroid injections, or cyst aspiration may offer temporary relief, surgical excision combined with fusion provides the best long-term outcomes by addressing both neural compression and underlying spinal instability, thereby minimizing recurrence risk. (Study of surgical management of lumbar synovial facet cyst – See PubMed.)

Who Performs This Treatment? (Specialists and Team Involved)

Treatment is provided by orthopedic spine surgeons or neurosurgeons, often working with pain management specialists, radiologists, and physical therapists.

When to See a Specialist?

Consult a spine specialist if you experience:

• Persistent back or leg pain

• Numbness or weakness in the legs

• Pain that worsens while standing or walking

When to Go to the Emergency Room?

Seek immediate care if you develop:

• Loss of bladder or bowel control

• Severe leg weakness or numbness

• Sudden worsening of pain after a fall or injury

What Recovery Really Looks Like?

After surgery, most patients experience immediate improvement in leg pain and mobility. Physical therapy helps strengthen the back and prevent recurrence. Return to normal activity is typically possible within 4–8 weeks.

What Happens If You Ignore It?

Ignoring a symptomatic facet cyst may lead to chronic pain, nerve damage, or worsening spinal stenosis. Early diagnosis and treatment improve outcomes.

How to Prevent It?

• Maintain good posture and spinal alignment.

• Exercise regularly to strengthen core and back muscles.

• Avoid repetitive twisting or heavy lifting.

• Manage arthritis and maintain a healthy weight.

Nutrition and Bone or Joint Health

A diet rich in calcium, vitamin D, and omega-3 fatty acids supports bone health and reduces inflammation. Staying hydrated keeps spinal joints lubricated.

Activity and Lifestyle Modifications

Engage in low-impact exercises such as swimming, yoga, or walking. Avoid high-impact activities that strain the back. Regular stretching maintains flexibility and reduces stress on the facet joints.

Do you have more questions?