Articulations of the Vertebral Column

Adjacent vertebrae from C2 to S1 articulate at two regions: the vertebral bodies connect via a symphysis, a cartilaginous joint made of fibrocartilage, while the articular processes form zygapophysial joints, which are synovial plane joints. Together, these structural joints synovial joints enable anterior, posterior, and lateral bending plus rotational movement of the spine.

Intervertebral joints allow anterior, posterior, and lateral bending of the body along with rotational movement. The range of motion varies by region: cervical and lumbar regions permit extensive flexion, extension, and lateral flexion, while the thoracic region has limited motion due to overlapping spinous processes and the attached thoracic cage.

The atlas (C1) and axis (C2) connect via the atlantoaxial joint, which consists of three articulations. The dens projects upward from the axis body and pivots within the anterior arch of the atlas, held by a strong posterior ligament. This pivot joint allows the atlas to rotate on the axis, enabling head rotation side to side.

The atlanto-occipital joint forms between the superior articular processes of the atlas and the occipital condyles on the skull base. Its U-shaped curvature oriented along the anterior-posterior axis allows the skull to rock forward and backward, producing head flexion and extension, and also enables up-and-down head movement.

The orientation of articular processes at zygapophysial joints determines available motions in each vertebral region. Cervical vertebrae have flattened processes facing upward or downward, permitting extensive flexion, extension, lateral flexion, and rotation. Lumbar processes allow considerable flexion, extension, and lateral flexion but prohibit rotation due to their orientation.

Thoracic vertebrae form synovial plane joints with the ribs, which are classified as structural joints synovial joints. These articulations allow gliding movement of the ribs during respiration, enabling the rib cage to expand and contract while breathing and facilitating efficient gas exchange.

The sacrum articulates with the ilium of the pelvis, forming the sacroiliac joint. This articulation connects the vertebral column to the pelvic girdle, providing structural stability and transmitting forces between the spine and lower limbs during weight-bearing and movement activities.