Joints of spine (overview)

The spine forms the central axis of the human body and is composed of 33 small bones called vertebrae, which are separated by fibrocartilaginous structures known as intervertebral discs. The spine extends from the base of the skull to the tip of the coccyx. All vertebrae are interconnected and held in place by various joints that allow for a wide variety of movements.

The spine contains all types of joints - fibrous joints, cartilaginous joints, and synovial joints.

 

Fibrous joints of spine

Fibrous joints connect bones using fibrous connective tissue. They allow slight movements and do not have joint cavities. This joint type is divided into two main subtypes - sutures and syndesmoses.

The fibrous joints within the spine are classified as syndesmoses. These joints connect two or more bones through ligaments or membranes. The ligaments of the spine can be further categorized into long or short ligaments, or grouped by their location into those associated with the vertebral bodies and those associated with the vertebral arches.

Ligaments of the vertebral bodies include the following:

Ligaments of the vertebral arches are as follows:

The spine also has several specific short ligaments located at the level of its connection with the skull. These ligaments are known as the craniovertebral ligaments. They strengthen the three craniovertebral joints, which are situated between the first cervical vertebra (C1), the second cervical vertebra (C2), and the occipital bone of the skull.

These craniovertebral ligaments include the following:

 

Cartilaginous joints of spine

Cartilaginous joints are articulations that connect two bones with either hyaline or fibrous cartilage. Depending on the type of cartilage, cartilaginous joints can be further subdivided into primary and secondary cartilaginous joints.

The spine contains only the secondary cartilaginous joints that are also known as symphyses. These joints are made up of fibrocartilage and are located between the vertebral bodies.

The symphyses of the spine are as follows:

 

Synovial joints of spine

The spine also contains several synovial joints, which provide the broadest range of movements and are classified as diarthroses. Synovial joints feature a joint cavity that is enclosed by a joint capsule. Inside the capsule, the joint is lined with a synovial membrane that produces synovial fluid, which acts as a lubricant for smooth movement.

The spine has the following synovial joints:

  • Atlanto-occipital joints
  • Atlanto-axial joints
  • Facet (zygapophyseal) joints
  • Sacroiliac joints
  • Joints of head of rib
  • Costotransverse joints