All thoracic vertebral levels consist of three joints. There is one joint consisting of the intervertebral discs which connect the bodies of the vertebra. There are also two posterior and lateral joints with one on each side called facet joints. The facet joints provide support, stability and facilitate motion of the thoracic spine.
Facet joints are synovial joints, which have a smooth shiny contact surfaces called articular cartilage. The articular cartilage allows the bones to slide freely over each other with reduced friction and stress. Each joint is also surrounded by a protective sleeve called a capsule, and is lubricated by synovial fluid. The facet joints can become irritated and inflamed producing pain and dysfunction.
Each thoracic vertebra has a pair of ribs, one on each side. The twelve ribs form the thoracic cage and serve to protect the vital organs of the body (lungs, heart, liver, kidneys etc.) The nerves of the thoracic spine provide sensory and muscle innervations to the trunk and part of each arm. Additionally, the internal organs of the body supply these nerves.
The thoracic spine has less movement than the cervical and lumbar spine. The greatest amount of movement is forward bending or flexion. The ribs limit side bending and rotational, or turning, motions of the mid back.