AbstractObjectiveTo develop arthroscopic approaches to the atlanto‐occipital (A‐O) and describe associated arthroscopic anatomy.Study designExperimental ex vivo study and clinical case report.AnimalsTen equine cadaver joints and 1 clinical case.MethodsCT arthrograms of 8 A‐O joints were performed to determine the placement of an arthroscopic portal. Arthroscopy was performed via dorsal and/or ventral approaches (dorsal or ventral to the longissimus capitis tendon) in 10 cadaveric A‐O joints and the A‐O joint of a 2‐week‐old foal with septic arthritis. Accessible cartilage was debrided in 3 cadaver joints. Accessibility and risks were assessed by review of arthroscopic images, postoperative necropsy, and computed tomography (CT).ResultsDorsal and ventral outpouchings of the A‐O joint were identified with CT. Arthroscopy of the dorsal pouch provided access to 50% of the dorsocranial occipital condyle and 15% of the dorsocranial atlas articular surfaces. Joint distension caused displacement of the dura. Dura perforation occurred with a blind dorsal approach in 2 of 5 joints. Dura perforation did not occur after ultrasonography‐guided approaches. Arthroscopic debridement of septic arthritis and osteomyelitis was successful in 1 clinical case.ConclusionApproaches to the A‐O joint were determined from CT examinations. The cranial aspect of the dorsal pouch of the A‐O joint was accessed via arthroscopic triangulation in all horses of this study. Ultrasound‐guided joint access prevented perforation of vital structures, including the spinal canal.Clinical significanceAdvanced imaging improves the diagnosis of A‐O joint pathology. Descriptions of arthroscopic anatomy and accessibility provide important information for surgical intervention.