Costovertebral joints are found in the upper back between the vertebrae of the thoracic spine and the posterior ribcage. There are 12 thoracic vertebrae and 12 corresponding ribs. The costovertebral joints are found on either side of the vertebrae, where the end of each rib attaches between two adjacent vertebrae. A type of joint called an arthrodial or gliding joint, the costovertebral joint allows the head of the rib to rotate and slide slightly against the vertebra as the ribcage expands during inhalation.
On either side of the body of each thoracic vertebra is a pair of half-moon-shaped concavities called demi-facets, one at the top of the vertebral body and one at the bottom. Since adjacent vertebrae are stacked upon one another, the demi-facet at the bottom of one vertebra lines up with a mirrored demi-facet at the top of the next vertebra to form a round socket. This is where the head of the rib lines up, staggered between two adjacent vertebra.
Additionally, a projection emanating from the sides of the vertebrae immediately behind the costovertebral joints, known as the transverse process, is linked to the rib by the dorsal costotransverse ligament, forming the costotransverse joint. This ligament attaches on one end to what is referred to as the neck and tubercle of the rib, surfaces to either side of the spine on the posterior or rear aspect of each rib. The other end of the ligament directs backward and inward, attaching along the length of the transverse process on its anterior or front side. In doing so, it holds the back side of the rib in place against the front side of the parallel transverse process to either side of the spine.
Several ligaments connect the ribs and vertebrae at the costovertebral joints, holding the head of each rib against the vertebrae and supporting joint movement. These include the capsular ligament, the radiate ligament, and the interarticular ligament. The capsular ligament forms a circle around the head of the rib like a crown and attaches it to the rim of the round facet formed by the bodies of the adjacent vertebrae. Radiating off the front side of the head of each rib and attaching to the vertebral body in front of it is the radiate ligament, which extends from the head of the rib like the roots of a tree penetrating the ground in a circle around its trunk. The interarticular ligament, on the other hand, is found within the costovertebral joints, connecting the head of the rib to a flattened disk of cartilage between it and the facet of the vertebra.