Atlanto‐occipital joint

Type: ‐ Synovial joint of Ellipsoid variety

 Articular surface‐

• Above: convex occipital condyles

• Below: Concave superior articular facet of  atlas

       Important relation of atlas: Inferolateral free margin of altas arches over the vertebral artery and first cervical nerve

•       Blood supply: Vertebral artery

•       Nerve supply of joint:  C1 nerve

•       Movements of joint:

•       • Ellipsoid joint ( biaxial joint)

•       • Flexion / extension (nodding)‐ transverse axis

•       • Lateral flexion‐ antero-posterior axis

•       The atlantoaxial joint :

•       is a joint in the upper part of the neck between the first and second cervical vertebrae; the atlas and axis.

•       The atlantoaxial joint is of a complicated nature. It consists of three joint:

•       Comprise of

•       A pair of lateral atlantoaxial joints: (Plane joint) between inferior facets of atlas and superior facets of axis.

•        A median atlanto-axial joint: (pivot joint) between the dens and anterior arch and transverse ligament of atlas

•       Movements:

•        All three joints produce rotatory movement around a vertical axis (No movement)

•        Movement is limited by alar ligament

•        Muscles producing movement are: Rectus capitis posterior major, obliquis capitis inferior, splenius capitis of one side along with sternomastoid of other side

(The median atlantoaxial joint is sometimes considered a double joint:

•       one between the posterior surface of the anterior arch of atlas and the front of the odontoid process

•       one between the anterior surface of the ligament and the back of the odontoid process)  

The ligaments connecting these bones are:

1. Articular capsules
2. Anterior atlantoaxial ligament
3. Posterior atlantoaxial ligament
4. Transverse ligament of the atlas