Which ligaments fix the dens of the axis?

The ligamentous apparatus of the median atlantoaxial joint includes the transverse ligament of the atlas, the alar ligaments, and the apical ligament of the dens. The transverse ligament of the atlas passes posterior to the dens to hold it in place.

What type of joint is the atlanto-occipital joint?

It is a biaxial condylar (ellipsoid) joint. Anatomically it is paired, but both parts always function synchronously.

Which ligaments stabilize the dens of the axis in the median joint?

The dens is secured by the transverse ligament of the atlas (against which its posterior surface rests), as well as the alar and apical ligaments.

What is the function of the lateral atlantoaxial joints?

They are plane joints combined with the median joint. Their primary role is to provide surface gliding during right and left head rotation.

Atlanto-Occipital & Atlantoaxial Joints: Anatomy & Biomechanics

Atlanto-Occipital and Atlantoaxial Joints

Articulatio atlantooccipitalis / Articulationes atlantoaxiales

For medical students2 min readUpdated 2026-10-10

The connection between the skull and the cervical spine forms a unified biomechanical complex. It provides complex head mobility, relying on the unique structure of the first two cervical vertebrae and the occipital condyles.

Synchronous actionThe paired atlanto-occipital joints always function together as a single mechanism

Axes of movementThe atlanto-occipital joint is biaxial, whereas the median atlantoaxial joint is uniaxial

Joint typesThe complex includes ellipsoid, pivot (trochoid), and plane joints

Main ligamentThe transverse ligament of the atlas lies against the posterior surface of the dens of the axis

Atlanto-Occipital Joint

This articulation (articulatio atlantooccipitalis) is responsible for attaching the skull to the vertebral column.

Articular Surfaces:

Superiorly, the joint is formed by the occipital condyles (condyli occipitales).
Inferiorly, they articulate with the superior articular surfaces of the first cervical vertebra, the atlas (facies articulares superiores atlantis).

A critical feature of this joint is its paired nature. Anatomically, these are two separate joints (right and left), but biomechanically they form a single entity and always function together.

In shape and biomechanics, this is a condylar (ellipsoid) joint. It has two axes of movement, allowing for the following actions:

Flexion and extension of the head (nodding movements).
Slight lateral flexion of the head to the sides (right and left).
Circumduction, which is a combination of the movements described above.

Median Atlantoaxial Joint

This joint (articulatio atlantoaxialis mediana) forms the central pivot for head rotation. It is located between the first (atlas) and second (axis) cervical vertebrae.

Articular Surfaces are represented by:

The anterior articular surface of the dens of the axis (facies articularis anterior dentis).
The facet for the dens located on the anterior arch of the atlas (fovea dentis atlantis).

Additionally, the posterior articular surface of the dens of the axis tightly apposes the transverse ligament of the atlas.

According to classification, this is a pivot (trochoid/cylindrical) joint. It is uniaxial: movement occurs exclusively around a vertical axis passing strictly through the dens of the axis. The primary function of this articulation is to enable rotation of the head to the right and left.

Stability of this vital junction is maintained by a robust ligamentous apparatus:

Transverse ligament of the atlas (lig. transversum atlantis).
Alar ligaments (ligg. alaria).
Apical ligament of the dens (lig. apicis dentis).

Lateral Atlantoaxial Joints

The paired lateral joints (articulationes atlantoaxiales laterales) complement the function of the median joint.

They are formed by the following articular surfaces:

Inferior articular surfaces of the atlas (facies articulares inferiores atlantis).
Superior articular surfaces of the axis (facies articulares superiores axis).

Structurally, these are plane joints. Their action cannot occur in isolation—they are always combined with the median atlantoaxial joint.

During head rotation, these joints facilitate smooth sliding of the articular surfaces relative to each other, ensuring the unhindered participation of the entire complex in rotating the head around the dens of the axis.

Mnemonic

To easily remember the functions: in the atlanto-occipital joint we "nod" (flexion/extension), while in the atlantoaxial joints we "shake our head" (rotation around the dens).

Frequently asked questions

Which ligaments fix the dens of the axis?: The ligamentous apparatus of the median atlantoaxial joint includes the transverse ligament of the atlas, the alar ligaments, and the apical ligament of the dens. The transverse ligament of the atlas passes posterior to the dens to hold it in place.
What type of joint is the atlanto-occipital joint?: It is a biaxial condylar (ellipsoid) joint. Anatomically it is paired, but both parts always function synchronously.
Which ligaments stabilize the dens of the axis in the median joint?: The dens is secured by the transverse ligament of the atlas (against which its posterior surface rests), as well as the alar and apical ligaments.
What is the function of the lateral atlantoaxial joints?: They are plane joints combined with the median joint. Their primary role is to provide surface gliding during right and left head rotation.

Go deeper

Topography of the articular surfaces of the occipital condyles and the atlas
Mechanism of synchronous function of the right and left atlanto-occipital joints
Detailed structure of the transverse ligament of the atlas and its role
Biomechanics of gliding in the lateral atlantoaxial joints during maximal rotation