The facet joints are joints in the spine located in the back (posterior) aspect of the spine. There are facet joints at each vertebral level, one on each side of the spine. These joints provide flexibility (allow the spine to turn or bend with movement) and stability (prevent excessive motion). Facet arthritis happens when the cartilage that covers the ends of the joints wears out and becomes thin. This can contribute to the growth of osteophytes (bone spurs) and hypertrophy (enlargement) of the joints.

Facet arthritis can be associated with pain and stiffness. The pain from an arthritic facet joint is often felt in the spine near the joint, but it can also refer to other locations. For example, pain from cervical (neck) facet arthritis may radiate toward the back of the head, ear, or shoulder. Pain from lumbar (low back) facet arthritis may radiate toward the buttock, hip, or thigh. The pain is often worse with certain movements or after a period of inactivity or sleep.

Risk factors for facet arthritis include age, history of trauma, degenerative disc disease, poor posture, and family history of degenerative arthritis.  

A careful history and physical examination is often enough to diagnose facet arthritis as a potential cause of pain. Imaging of the spine (X-ray, CT scan, MRI) can also show changes consistent with facet arthritis. If it is not clear that the facet joint is causing the pain, a diagnostic (anesthetic) injection of the facet joint can provide valuable diagnostic information.