A 41-year-old female presents to clinic with complaints of neck pain ongoing for a few months. She states the pain has come on gradually and is now getting in the way of her daily activities. She denies any radiation of the pain and rates it a 5/10. Vitals are within normal limits. Osteopathic structural examination reveals that her C1 vertebrae has more motion when translating to the right. Given the physical exam findings, which of the following best describes the OA joint?