Each vertebra is made of two major structures. The front portion is a thick, square shape piece of bone known as the vertebral body. A bridge of bone then branches off the back of the vertebral body to form a ring like structure known collectively as the “posterior elements.” This ring provides additional stability to the spine, while providing a protective shield of bone around the spinal cord and spinal nerves.
A facet joint then serves to connect each vertebra. The disc is a soft donut shaped piece of connective tissue that connects the vertebral bodies, provides cushion and support during spine loading, and allows for a certain degree of range of motion between the vertebral bodies. The facet joints connect the posterior ring of bones that branch off the vertebral body. As mentioned, two facets exist between each vertebra, one on the right and one on the left.
Facet joints exist in all portions of the spine (cervical, thoracic, and lumbar). Each facet joint is built similar to most other joints in the body. The facets are lined with a thin layer of cartilage, surround by a capsule of connective tissue, and contain a small amount of joint fluid to keep the joint lubricated. Just like other joints in the body, facet joints can become irritated due to a variety of reasons. These include aging, injury, and mechanical overload. Facet joint injections can, therefore, be useful to diagnosis and treat painful conditions affecting the facet joint.