What a facet joint is, and why it hurts

Each vertebra meets the one below it at three points: the disc in front and a pair of small synovial joints behind, one on each side. Those paired joints — the facets, or zygapophysial joints — guide and limit motion. They are true joints, with cartilage, a capsule and a nerve supply, and like any other joint they can wear, inflame and hurt.

Each facet joint is innervated by the medial branches of the dorsal rami from the level above and the level at which it sits. That double supply is the anatomical fact the whole diagnosis rests on: to anesthetize one joint you have to block two nerves, and if blocking those two nerves abolishes the pain, the joint they serve was the generator.

Why imaging cannot answer this

Facet arthropathy shows on CT and MRI, and it shows in enormous numbers of people who have no back pain at all. Its prevalence climbs steeply with age, which means that in anyone past their forties a report of facet degeneration is describing a normal finding for that decade rather than a cause of symptoms.

The reverse is also true and less well known. A facet joint can be a florid pain generator with an unremarkable appearance on imaging, because inflammation of a capsule and sensitization of a medial branch have no radiographic signature. So the scan produces false positives in the people who do not hurt and false negatives in the people who do — which is a fairly complete description of a test that should not be used to make this diagnosis.

What facet pain feels like

• Axial rather than radiating — across the low back, often to one side, sometimes referring into the buttock or the back of the thigh, but characteristically not below the knee.
• Worse with extension — standing for a while, walking downhill, reaching up, arching back. The facets are load-bearing in extension and unloaded in flexion.
• Worse getting up from a chair or out of a car, and easier once you are moving.
• Morning stiffness that eases within thirty minutes or so, then returns as the day accumulates.
• Tender over the joint line a couple of centimeters off the midline, at the level involved.

Every one of those features overlaps with something else. That is not a flaw in the description; it is the reason the clinical picture alone is not sufficient and the block exists. The examination narrows the field to a level or two. The block settles it.

How it is actually diagnosed

Why this joint fails in the first place

The mechanical account is straightforward and incomplete. As a disc loses height, the facets behind it are pushed into closer contact and take a larger share of the load than they were designed for. Years of that produces capsular thickening, cartilage loss and an inflamed, sensitized joint. Sustained extension postures and repetitive lifting accelerate it.

The account that gets left out is what the joint is made of. Facet cartilage and capsule are collagen, and collagen in a state of chronic hyperinsulinemia is glycated and cross-linked — stiffer, less able to distribute load, slower to turn over. Metabolic inflammation keeps the joint in a degradative rather than a reparative state, so the microdamage from an ordinary week does not fully clear before the next week begins. The same lifting job, in two people, produces a failed facet joint in the one whose tissue could not keep up with the repair debt.

And the third layer, which belongs on this page because it is a cause and not a footnote: the schedule. Rotating shifts and short sleep suppress the slow-wave phase when tissue repair is concentrated, and the food that is available at the end of a late shift is engineered around acellular carbohydrate. That is not a lifestyle aside. It is the reason the tissue was in deficit before the load arrived.

What treatment actually looks like

If the block confirms the facets, radiofrequency neurotomy interrupts the medial branches and the joint stops reporting. The relief lasts until those nerves regenerate, which is typically a matter of many months, and the procedure can be repeated when it does. It changes nothing structural about your spine, which is precisely its advantage over the alternatives.

What the procedure does not do is fix the reason the joint became a pain generator. That is the work the quiet window is for: reconditioning the extensor mass so the passive structures carry less, restoring extension tolerance rather than avoiding extension forever, and addressing the metabolic terrain so collagen turnover is not running at a deficit. The behavioral component of that is delivered here in-house by a licensed pain-trained clinician, because a program handed over as a referral is a program that does not happen.

Steroid injection into the facet joint is a different and generally weaker option than the medial branch pathway, and we will tell you when it is worth doing rather than defaulting to it.

Common questions

How do I know it is facet and not disc?

Broadly: facet pain is worse in extension and better in flexion, disc pain is worse in flexion and sitting and better standing. Facet pain is axial and stops around the knee; disc-related nerve root pain runs past it in a defined line. But the overlap is real, which is why the answer comes from a block rather than from a description. The disc question, in full.

Will a facet block cure me?

A diagnostic block is a test, not a treatment, and it is deliberately short-acting. Its job is to tell us whether the joint we suspect is the joint that hurts. The durable treatment is the neurotomy that follows a positive result.

There is more on this in Durable relief for facet pain, if the right nerves were identified first..

How many injections will I need?

There is no set course, and anyone offering you a package of three has decided the answer before examining you. Quantity here is a clinical decision made against what the previous procedure achieved.

Your scan described a back that belongs to somebody your age. explains what that looks like.

Is radiofrequency ablation permanent?

No, and that is by design. The medial branches regrow, which is why the effect wears off and why the procedure is repeatable. A permanent lesion of a nerve is a much bigger commitment with a much longer list of ways to be wrong.

The mechanism is covered in The only test that finds facet pain. There is no scan for it..

Can facet pain go away on its own?

An acute facet sprain frequently does. A joint that has been generating pain for months, on a spine that has been redistributing load for years, generally does not resolve without something changing — either the load, the terrain, or the signal.

You have explained it four times. Nobody wrote it down. explains what that looks like.

Related reading

• The diagnostic block, explained
• Radiofrequency neurotomy
• What your MRI actually showed
• Sacroiliac joint pain
• Back pain doctor in St. Louis

A vertebra that has slipped forward changes which structures carry the load.