What Is a Facet Joint?


Quick Answer

A facet joint, also called a zygapophysial joint, is a joint connecting one vertebra and another. There are four facet joints at the back of a vertebra, and they're found on the extensions of the bone. These joints don't allow freedom of movement so much as they restrict movement; because of this, they protect the body from injuries like hyperextension and whiplash.

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What Is a Facet Joint?
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Full Answer

Each vertebra has two superior articular facet joints and two inferior articular facet joints. The former is right on top of the latter. When a person is trying to move his or her spine in ways that might be dangerous, the joints act like a door hinge to keep the spinal column from going any farther than it should.

These joints are protected by collagen, cartilage and synovial fluid, which keeps them lubricated and easy to move. The spinal nerves also pass through the facet joints.

Because of their role in helping the body move in safe ways, the facet joints are especially subject to wear and tear. The facet joints in the lower back are a common place for a person to experience facet joint arthritis. The degeneration of the joints also might compress the spinal nerves and cause further pain.

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