Facet joint syndrome

In one minute

Facet joint syndrome is low back pain from the small paired joints at the back of each spinal segment. It is a condition of middle and later life. The pain sits in the lower back, spreads into the buttock or thigh but rarely below the knee, is worse on bending backward, and does not cause true numbness or weakness. The diagnosis rests on a test injection, the medial branch block, not on a scan. Treatment is exercise and time for most people, radiofrequency denervation for some, and surgery only when the worn joints have caused a second problem.

What it is

Each lumbar segment has three joints: the disc at the front and two facet joints at the back. The facets are true joints, with cartilage, a lining that makes fluid and a capsule, and they wear the way a knee or a thumb joint wears.

Reports in this region usually call the wear "spondyloarthrosis"; English-language reports say "facet arthropathy" or "facet joint osteoarthritis". All describe the same thing. Whether the worn joint is the source of the pain is a separate question.

Each joint is supplied by two small nerves, the medial branches from its own level and the level above. They carry pain from the joint and supply the deep back muscles, and they are the target of both the diagnostic block and the denervation.

Causes and risk factors

Estimates of how much chronic low back pain comes from the facet joints vary with the method. A review in Anesthesiology puts it at up to 15% of patients with chronic low back pain; higher figures in the literature come from studies using diagnostic blocks, and depend on the cut-off and the number of blocks used.

Age is the strongest association. On imaging, moderate to severe facet arthropathy is present in 36% of adults under 45, 67% of those aged 45 to 64 and 89% of those over 65, though most of these people have no pain. Other associations are disc degeneration at the same level, being overweight, and spondylolisthesis. According to the 2020 consensus guideline, L5-S1 is the joint most often responsible for pain and L4-L5 the one most often worn on imaging.

How it develops

The cartilage thins and cracks. Bony spurs (osteophytes) grow at the edges, the joint space narrows and the capsule thickens. The lining can inflame, and the capsule can bulge into the canal as a synovial cyst. Because the medial branches supply both the joint and the muscles beside it, an irritated joint produces pain felt deep in the back and referred, without a clear border, into the buttock and the back of the thigh. It is not a pinched nerve, which is why the pain does not follow a single stripe down the leg and why strength and reflexes stay normal.

Symptoms

The pain is a dull, deep ache in the lower back, worse after sitting still and worse on standing straight, arching backward or twisting. It spreads into the buttock, groin or thigh and usually stops above the knee. Bending forward tends to ease it. Tenderness over the joints is common, but the reviews are clear that no examination finding confirms the diagnosis.

What separates it from a disc herniation with a trapped nerve is the absence of sharp pain below the knee, of numbness in a strip of skin, and of weakness.

Diagnosis

History and examination come first, mainly to rule out other causes of back pain. Imaging comes next, and its role is to exclude, not to confirm: the guidelines and reviews agree that worn joints on X-ray, CT (computed tomography) or MRI (magnetic resonance imaging) appear as often in people without pain as with it. NICE (the UK National Institute for Health and Care Excellence) says imaging must not be required before denervation. MRI is still worth having because it shows the things that change the plan: a cyst, a narrowed canal, a slip, a disc on a root.

The test that makes the diagnosis is the medial branch block. Under X-ray guidance a small volume of local anaesthetic is placed on the two nerves of the suspected joint. If the pain falls by more than half while the anaesthetic works, the joint is the probable source; that is the threshold the 2020 consensus guideline recommends, and some specialists ask for 80%. The block has a false-positive rate of 25% to 40%, which is why some specialists ask for two positive blocks on separate days; the consensus guideline recommends a single block, with one of its societies dissenting on that point and on the cut-off. NICE requires a positive block before any denervation.

If you send images for an opinion, include the MRI, its report and any X-rays, and describe where the pain goes and what makes it worse.

Treatment without surgery

Most facet joint pain is managed without any procedure. NICE supports continued normal activity, a group exercise programme, and manual therapy only as part of a package that includes exercise; it advises against belts, corsets, traction, acupuncture, TENS (transcutaneous electrical nerve stimulation) and ultrasound. Physiotherapy concentrates on posture, stretching and the deep trunk muscles. Short courses of anti-inflammatory medication (NSAIDs) are used for flares at the lowest dose for the shortest time.

Steroid injections into the joint itself give short to intermediate relief in some people, but the Anesthesiology review calls the evidence conflicting and the consensus guideline finds the medial branch block a better predictor of what will happen next.

Radiofrequency denervation is the main procedure. A probe heats the medial branches so they stop carrying pain; the relief is temporary and the procedure can be repeated. NICE advises considering it when non-surgical treatment has failed, the pain is moderate or severe (5 or more out of 10) and a diagnostic block was positive. The evidence on how well it works is mixed. The Cochrane review of 2015 found moderate-quality evidence of a greater short-term effect on pain than placebo and low-quality evidence of better function. The Mint trials of 2017, 681 patients in 16 Dutch pain clinics, found that adding denervation to a three-month exercise programme gave no clinically important improvement; in the facet joint trial the difference at three months was 0.18 points on a 10-point scale.

When surgery is considered

For facet joint pain on its own, surgery is not the answer. NICE advises against spinal fusion for low back pain outside a randomised trial, and there is no evidence that removing or fusing a painful facet joint reliably removes the pain.

Surgery is considered when the worn joints have produced a second problem that compresses a nerve: a synovial cyst, a narrowed canal with neurogenic claudication, a narrowed foramen with single-root pain, or a degenerative slip with nerve symptoms. It is also considered when a nerve is losing strength or, urgently, when bladder or bowel control is affected. In each case the operation is aimed at the nerve, not at the back pain.

Surgical options

There is no operation for isolated facet pain that the evidence supports. The procedures here treat what facet degeneration causes.

Endoscopic decompression opens a narrowed canal or foramen through a 7 mm incision, trimming the overgrown joint edge and ligament while keeping the joint itself. Endoscopic facet cyst removal takes a synovial cyst off the nerve through the same kind of incision. Fusion, endoscopic or open, is reserved for an unstable segment, most often a mobile spondylolisthesis, and comes with the cost of a stiff level.

How we treat it at spine.uz

Send the MRI and the report; a doctor from the team replies by voice within 48 hours, free of charge. For most people with facet joint pain the honest answer is that this is not a surgical problem, and the useful part of an opinion is what the scan shows and what the next sensible step is: exercise, a medial branch block, or denervation in a pain clinic.

When the worn joints have trapped a nerve and surgery is indicated, the operation is an endoscopic decompression or cyst removal through a 7 mm incision, with no screws or implants. Most endoscopic decompressions are done without general anaesthesia, under local anaesthesia with sedation; the anaesthetist and surgeon decide per patient. Most patients walk on the day of surgery and go home within 24 hours. Every patient receives a written conclusion from the team. Across 27,600+ endoscopic and spine operations, the team's complication rate is well below 1%.

Recovery and outcomes

The joint changes on imaging progress with age, but the pain does not have to progress with them. Exercise programmes improve function, and NICE asks clinicians to promote a return to work and normal activity rather than rest.

After radiofrequency denervation, in people selected by a positive block, relief lasts 6 to 12 months in those who respond, and a repeat is possible when the pain returns. In the Mint trials, adding denervation to exercise gave no clinically important improvement over exercise alone.

When surgery has been done for a nerve trapped by the worn joints, the leg symptoms are the ones expected to improve; the back ache from the joints themselves may remain, and a patient should hear that before the operation.

Living with it and prevention

Keep moving; long periods sitting still and long periods standing arched backward both provoke the joints. A daily routine that keeps the trunk muscles working is the treatment NICE supports. Do not chase repeated scans: the joints will look worse each decade whether or not they hurt.