The joints and their alignments.

<p>A) The ball-and-socket joint between occiput (left) and atlas (right). The ball is marked green. The socket is marked red. B) The pivot joint between the atlas (left) and axis (right). The pivot is marked red. The ring-like socket is marked green. C) The saddle joint between C14 (left) and T1 (right). The convex area of C14 is marked red. The convex area of T1 is marked green. D) The saddle joint between C14 and T1. The two coordinate systems are shown. Additionally a zygapophyseal joint is marked with a red circle.