The atlantooccipital (AO) joints uniquely connect the cervical spine (C1, the atlas) to the occiput base. AO joints are condyloid joints. Unlike the lower cervical segments, AO joints lack corresponding cervical discs and uncinate processes. In addition, AO joints lie anterolateral to the spinal cord (SC; rather than posterolateral), and they align with the uncinate processes of the lower cervical bodies. AO joints are very mobile joints with primary ligamentous stabilization, and they are considered to be synovial joints with capsules. The joints facilitate occipital flexion and extension of the atlas (C1).

Patients with AO joint pain often complain of unilateral suboccipital pain that can refer to the occipital and temporal regions but does not include the vertex. This pain can occur after flexion and extension injuries.

Injection into the AO joint can be a challenging endeavor given the proximity of nearby vital neurovascular structures. Familiarity with the regional anatomy will minimize the adverse risks of potentially catastrophic consequences.

The ipsilateral oblique trajectory view and multiplanar imaging allow for safe needle placement into the AO joint, avoiding the vital neurovascular structures. It is crucial to precisely target the lateral one-third of the AO joint because straying too far medially, laterally, or inferiorly can have devastating consequences.