An apparatus comprises a base configured to mount on a frame, a post coupled to the base and extending upwardly therefrom, a head support for supporting the head of a patient lying in a prone position on the frame, and a lockable joint coupled to the post and coupled to the head support to position the head support above the base. The lockable joint, when locked, prevents movement of the head support along the post and prevents movement of the head support relative to the post about a plurality of axes. The lockable joint, when unlocked, allows movement of the head support along the post and allows movement of the head support relative to the post about the plurality of axes.