[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Spine](https://durgical.com/en/anatomy/region/spine/) › Skull–atlas joints [Joints and ligaments](https://durgical.com/en/anatomy/system/joints-and-ligaments/) · [Spine](https://durgical.com/en/anatomy/region/spine/) # Skull–atlas joints The atlanto-occipital joints are the two joints between the skull and the atlas (C1); they let the head nod "yes". Official name: Atlanto-occipital joint [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=spine&select=atlanto_occipital_joints&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The two joints between the skull and the atlas. ## What it does Allow nodding 'yes' (about 25° of bending forward and back) and very little turning. ## Key points - Stability comes mainly from ligaments that join the skull to C2 (tectorial membrane, alar ligaments), not from the loose joint capsules - Atlanto-occipital dislocation is a high-energy, often fatal injury; children are more prone because of their large head and flatter, smaller condyles - The vertebral artery and the suboccipital nerve (C1 dorsal ramus) pass under the lower free edge of the posterior atlanto-occipital membrane, on the posterior arch of the atlas ## Key facts **Where** Occipital condyles on the concave superior facets of the atlas lateral masses (C0–C1) **Attaches** Loose fibrous capsules; anterior and posterior atlanto-occipital membranes **Function** Synovial condyloid (ellipsoid) joints; nodding flexion-extension (about 25°) and slight side bending, almost no rotation ## Relations **Above** Occipital condyles of the [occipital bone](https://durgical.com/en/anatomy/occipital-bone/) on each side of the [foramen magnum](https://durgical.com/en/anatomy/foramen-magnum/); the [hypoglossal canal](https://durgical.com/en/anatomy/hypoglossal-canal/) runs just above each condyle **Medial** Foramen magnum with the junction of the medulla and [spinal cord](https://durgical.com/en/anatomy/spinal-cord/), the vertebral arteries entering the skull and the [alar ligaments](https://durgical.com/en/anatomy/alar-ligaments/) **In front** Anterior atlanto-occipital membrane, rectus capitis anterior and [longus capitis](https://durgical.com/en/anatomy/longus-capitis-muscle/); in front of them, the retropharyngeal space and the [pharynx](https://durgical.com/en/anatomy/pharynx/) **Behind** Posterior atlanto-occipital membrane and the suboccipital triangle (rectus capitis posterior major, obliquus capitis superior and inferior) with the [vertebral artery](https://durgical.com/en/anatomy/vertebral-artery/) in its groove **Below** Lateral masses of the [atlas (C1)](https://durgical.com/en/anatomy/atlas/), whose lower facets form the lateral atlantoaxial joints ## On imaging CT with sagittal and coronal reformats shows the condyle–C1 gap; widening or asymmetry suggests craniocervical dissociation. On a lateral view or CT, the basion–dens interval and the Powers ratio screen for dislocation (a Powers ratio above 1 suggests anterior dislocation). Condyle fractures are easily missed on radiographs and are best seen on CT. ## Common problems - Neck pain and headaches from arthritis or after whiplash. - Bone spurs that narrow the opening for a nerve root. ## How it is diagnosed There is no single sign. CT or MRI show arthritis; a numbing injection of the nerves to the joint (medial branch block) shows whether the joint is the pain source. ## Treatment - Physical therapy, medicine, injections; radiofrequency ablation for lasting facet pain. ## Clinical notes - Survivors of atlanto-occipital dislocation may have brainstem, lower cranial nerve or vertebral artery injury - Occipital condyle fractures (Anderson–Montesano types I–III) enter this joint; they are found on CT rather than plain films - In rheumatoid arthritis, erosion of these joints and the atlantoaxial joints lets the skull settle onto C1–C2, so the dens rises toward the foramen magnum (cranial settling) ## Anatomical variants - Occipitalisation (assimilation) of the atlas: partial or complete fusion of C1 with the occipital bone; uncommon, reported frequencies vary, and it may come with basilar invagination or a Chiari malformation, adding load to C1–C2 ## Development The condyles and the region around the foramen magnum come from the lowest occipital sclerotomes (the proatlas); faulty segmentation there explains atlas assimilation and a small extra bony knob in front of the foramen magnum (third condyle). ## Test yourself Think of the answer, then tap the question to see it. ## What type of joint are the atlanto-occipital joints, and what movement do they allow? Synovial condyloid (ellipsoid) joints between the occipital condyles and the atlas; they allow nodding flexion-extension (about 25°), with almost no rotation. ## What mainly stabilises the atlanto-occipital joints? Ligaments joining the skull to C2, the tectorial membrane and the alar ligaments, rather than the loose joint capsules. ## Why are children more prone to atlanto-occipital dislocation? Their head is large and their occipital condyles are flatter and smaller; the injury is high-energy and often fatal. ## On imaging, what does a Powers ratio above 1 suggest? Anterior atlanto-occipital dislocation; CT also shows widening or asymmetry of the condyle–C1 gap in craniocervical dissociation. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/atlanto-occipital-joint/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** articulatio atlantooccipitalis TA2 1630 **Official Spanish (DeCS)** Articulación atlantooccipital DeCS D001269 **English (TA2)** Atlanto-occipital joint **Also called** articulus atlantooccipitalis ## Related - [Atlas (C1)](https://durgical.com/en/anatomy/atlas/) - [Base of the skull](https://durgical.com/en/anatomy/occipital-bone/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=1276&filter=ths_termall&q=Articulaci%C3%B3n%20Atlantooccipital); [Anatomy, Head and Neck: Atlantoaxial Joint](https://www.ncbi.nlm.nih.gov/books/NBK563271/); [Anatomy, Head and Neck: Foramen Magnum](https://www.ncbi.nlm.nih.gov/books/NBK526041/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/atlanto-occipital-joint/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/atlanto-occipital-joint/