Lumbar facet cyst

A lumbar facet cyst is a small, fluid-filled bulge that arises from an arthritic facet joint at the back of the spine. As it enlarges, the cyst can press against a nearby nerve, producing leg pain that often feels much like the pain from a herniated disc. The distinction matters: unlike most disc herniations, facet cysts often don't resolve with conservative care, and when they need treatment, the surgical conversation is its own.

This page explains what a facet cyst is, how it produces symptoms, why some non-surgical treatments help temporarily but not durably, and what the surgical options look like — including whether fusion is necessary (usually it isn't).

What a facet joint cyst actually is

Facet joints are small joints at the back of each pair of vertebrae that allow the spine to bend and rotate. Like any joint, they can become arthritic over time, particularly in the lower back. As an arthritic facet joint produces more joint fluid than the small joint capsule can comfortably hold, the lining of the joint sometimes balloons outward into a pouch — a synovial cyst.

The cyst itself is typically only a few millimeters across. What makes it clinically important isn't its size but its location: facet joints sit right next to the spinal canal and the foramen where nerves exit. A small cyst growing forward from an arthritic facet often ends up pressing on the nerve root next door.

Most facet cysts that cause symptoms are at the L4–L5 level, where degenerative changes in the lower back are most common.

How a facet cyst causes leg pain

When a facet cyst compresses a nerve root, the result is radiculopathy — pain, numbness, tingling, or weakness in the area that nerve supplies. The pattern matches the affected nerve: an L4–L5 facet cyst typically compresses the L5 nerve, producing pain along the outer leg and into the top of the foot, sometimes with weakness lifting the foot or the big toe.

Two things make facet cyst pain distinctive. First, many patients also have significant back pain at the same level, because the underlying facet arthritis that produced the cyst is itself a source of pain. Second, the symptoms can fluctuate noticeably — the cyst can change size with activity or with small bleeds inside it, and patients sometimes describe sudden worsening episodes followed by partial improvement.

Why standard non-surgical treatments often don't last

The first non-surgical step for a facet cyst is usually some combination of physical therapy, anti-inflammatories, and an image-guided injection — either into the facet joint itself or into the epidural space near the cyst. Some surgeons or interventionalists will also attempt to aspirate the cyst contents through a needle, sometimes followed by a steroid injection at the same site.

These can help, sometimes substantially. But they have an underlying limitation: they don't address the source. The facet joint that produced the cyst is still arthritic, still producing fluid, and many cysts re-fill within months even after a technically successful aspiration. Steroid injections can calm the inflammation around the cyst for weeks to months at a time, but they don't make the cyst itself go away.

For patients whose symptoms keep returning after injections or aspirations, this isn't a failure of the procedure — it's the natural course of the underlying problem. The cyst is a downstream consequence of the joint above it.

When surgery is worth considering

Surgical evaluation is typically reasonable when:

• Symptoms have persisted or returned after a real trial of non-surgical care, including at least one well-targeted injection
• Pain or functional limitation is significantly impacting daily life
• There is progressive weakness in the leg or foot
• The cyst is large enough on imaging to plausibly account for the symptoms
• The pattern of symptoms matches the level where the cyst is

A few situations warrant urgent evaluation regardless of how long symptoms have been present: rapidly worsening weakness, loss of bladder or bowel control, or numbness in the area you would sit on. These can suggest serious nerve compression and should be assessed immediately.

Surgical options

Surgery for a facet cyst removes the cyst itself and the small portion of the facet joint where it originates. What varies among approaches is how much surrounding bone has to be removed to do it.

Each approach has appropriate uses. The right choice depends on the size and location of the cyst, the condition of the surrounding bone, and whether any underlying instability is present.

Avoiding fusion when possible

A common worry coming into a facet cyst consultation is whether a fusion will be necessary. For most isolated facet cysts without underlying instability, the answer is no.

The reason fusion sometimes enters the conversation is that open cyst resection occasionally requires removing enough of the facet joint that the segment becomes less stable, and a fusion is added to protect against that. The smaller-incision approaches — tubular and especially endoscopic — preserve more of the facet joint by approaching the cyst more directly, which makes fusion less often necessary.

Fusion is still the right answer in specific situations: when there's a slip at the level (spondylolisthesis) that's contributing to symptoms, when underlying alignment problems are present, or when the cyst has eroded the joint to the point that the segment is already unstable. In the absence of those features, removing the cyst without fusing the spine is often the right answer.

Recovery

Recovery from endoscopic cyst resection follows a generally predictable pattern:

Day of surgery

The procedure takes roughly an hour. You walk before going home, and most patients leave the surgery center within a couple of hours.

First week

Most patients describe leg pain as significantly improved within hours to days. Soreness at the small incision is generally mild.

Return to walking

Encouraged from day one.

Return to desk-type work

Often within a few days.

Return to higher-impact activity

Typically by four to six weeks, guided by individual progress.

Recovery from open or tubular cyst resection follows a similar arc but generally takes longer in the early phase.

The longer-term picture for cyst resection is generally favorable. The cyst, once removed, doesn't typically recur at the same site (though new cysts can develop at other levels over time, since the underlying facet arthritis is a process that affects multiple joints).

Choosing what's right for you

The right approach depends on the specific characteristics of the cyst on imaging, the condition of the surrounding bone, whether any instability is present at the level, and your overall situation. Some cysts are textbook candidates for endoscopic resection; others, particularly those with significant underlying instability, are better treated differently.

Endoscopic spine surgery is the focus of my practice. If you've been diagnosed with a lumbar facet cyst and are weighing whether to continue with injections, proceed with surgery, or understand whether a less invasive surgical approach might be a fit, I'd be glad to discuss the options at an appointment.