Joints
Facet joints (artt. zygapophysiales)
The paired joints between the inferior articular process of one vertebra and the superior process of the one below. They carry little weight but determine direction: the orientation of the joint surfaces prescribes per level which movement is possible.
- Joint type
- Plane joints (artt. planae) with a true capsule and synovium
- Body region
- Spine
- Latin name
- Articulationes zygapophysiales
Movements, axes and normal values
| Movement | Plane | Axis | Normal range | End feel |
|---|---|---|---|---|
| Flexion | sagittal | varies per level | widest in the cervical spine, more limited lumbar; the facets lie about 45 degrees oblique cervically and nearly sagittal lumbar | firm springy (ligament) |
| Rotation | transverse | longitudinal | generous thoracically, only a few degrees per lumbar segment because the facets are sagittal there | firm springy (ligament) |
| Lateral flexion | frontal | sagittal (anteroposterior) | always coupled with rotation; the direction of that coupling differs per spinal region | firm springy (ligament) |
- Close-packed position
- Maximal extension
- Resting (loose-packed) position
- Midway between flexion and extension
- Capsular pattern
- Lateral flexion and rotation equally limited, extension more than flexion.
- Arthrokinematics
- In flexion the inferior facet glides up and forward, in extension down and back. In lateral flexion the facet on the concave side glides down and the one on the convex side glides up. The capsule is richly innervated by the medial branch of the dorsal ramus, which makes this joint a genuine pain source.
- Stability
- Its own capsule, reinforced anteriorly by the ligamentum flavum, and the multifidi running directly across the joint segment by segment.
- Palpation
- Not directly palpable. Lumbar, project them about two to three centimetres lateral to the spinous process; posteroanterior pressure there is the usual way to provoke and mobilise the level.
- Clinical
- Facet osteoarthritis is a common source of low back pain that worsens with extension and rotation and eases on bending forward. Canal stenosis arises partly from hypertrophy of these joints. An acutely locked segment gives a sudden, sharp restriction in one direction.
- Source
- Speciële anatomie van het houdings- en bewegingsapparaat (HU, 2013); BOKS anatomie Levensfasen (HU, 2024)