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How does the joint between the skull and the first vertebra allow head movement?

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Front and back views of the human skeleton are shown side by side, with labeled bones including the skull, spine, ribs, pelvis, arms, legs, hands, and feet. Insets detail the bones of the foot and hand, highlighting major bone groups and anatomical terms. — human skeleton Front and back views of the human skeleton.

The joint between the skull and the first vertebra, known as the atlas, is formed by the occipital condyles. These articular surfaces on the occipital bone allow the skull to rest upon and move against the atlas, specifically facilitating a nodding motion.12

While this joint enables nodding, side-to-side head rotation is achieved differently: the atlas turns on the axis, which is the second vertebra located immediately below it.2