Zygapophyseal joints (facet joints)

The zygapophyseal joints, usually called facet joints, are the small paired joints at the back of the spine. Behind each pair of neighbouring vertebrae sit two of them, one on each side, formed where the lower articular processes of the vertebra above meet the upper articular processes of the one below. They are synovial joints: a fibrous capsule encloses cartilage-covered joint surfaces and a little lubricating fluid (Curtis et al., 2025).

What do facet joints do?

Two kinds of joint link neighbouring vertebrae. At the front, the vertebral bodies are joined through the intervertebral discs, which allow movement and carry most of the spine’s weight. At the back, the facet joints guide and limit the range of movement (Waxenbaum et al., 2026). They allow the spine to bend forwards and backwards while limiting rotation, and they stop the vertebrae slipping over one another. Their nerve supply comes from a small branch, the medial branch of the dorsal ramus (Curtis et al., 2025).

Their angle changes along the spine, and so does the movement they allow. In the lumbar spine the facet surfaces stand mostly upright and are curved (Waxenbaum et al., 2026). In the thoracic spine they face backwards and outwards, and the mid-thoracic levels, T5 to T8, rotate the most (Waxenbaum et al., 2026). Facet joints also bear some of the load in certain positions (Waxenbaum et al., 2026).

Can facet joints cause back pain?

They can, but proving it in any one person is hard. Estimates of how much chronic low back pain comes from the facet joints range from 15% to 41% (Curtis et al., 2025). Despite the old idea of a recognisable “facet syndrome”, a review found that neither the history nor a physical examination can reliably identify facet joint pain. The most accepted test is a diagnostic block, numbing the joint or its nerve with a small amount of anaesthetic, and even that gives many false positives (Cohen & Raja, 2007).

In the neck, the facet joints matter most after injury. In 50 people with chronic neck pain after whiplash, tested with double-blind blocks, 54% had painful facet joints, the most common source in that group (Barnsley et al., 1995).

For most desk workers with back ache, the pain is classed as non-specific low back pain, without a single structure to blame. Lower back pain from sitting covers that everyday picture, and Is it bad to crack your neck? answers a question people often ask about the joints of the neck.

What helps facet joint pain?

The first steps are the same as for other back pain: keep active and use exercise. The more specific treatment is radiofrequency denervation, which aims to stop the medial branch nerve sending pain signals. NICE says to consider referral for it only when non-surgical treatment hasn’t worked, the main source of pain is thought to be structures supplied by that nerve, and pain is moderate or severe; it should be done only after a positive diagnostic block (NICE). The NHS describes it as a procedure to seal off some of the nerves in the back, only for long-term lower back pain (NHS).

The trial evidence is not encouraging. In the Dutch MINT study, 251 people with chronic low back pain and a positive facet block all had a 3-month exercise programme; adding radiofrequency denervation made a difference of only 0.18 points on a 0 to 10 pain scale at 3 months, well below the 2 points the trial had set as clinically important (Juch et al., 2017).

When to see a doctor

See a GP if back pain doesn’t improve after a few weeks or is worse at night. Call 999 or go to A&E if it comes with numbness or weakness in both legs, loss of feeling around the genitals or anus, or changes in bladder or bowel control (NHS).