Atlas vertebra (C1)

The atlas vertebra is the first bone of the neck, C1, sitting directly beneath the skull. Unlike the vertebrae below it, it has no vertebral body and no spinous process. It is a ring made of a front arch and a back arch, joined on each side by a thick lateral mass, and those two lateral masses carry the weight of the head. Its name comes from Atlas of Greek mythology, who bore the world on his shoulders, as C1 bears the skull (Kenhub; TeachMeAnatomy).

How does the atlas vertebra move the head?

The atlas forms two sets of joints, and each has its own job (Kenhub; TeachMeAnatomy):

• Atlanto-occipital joints, for nodding. The upper surfaces of the lateral masses cradle two rounded knobs at the base of the skull. These joints allow the head to bend forward and back on the neck, plus a little side bending.
• Atlanto-axial joints, for turning. Below, the atlas meets the axis (C2) at three joints. A peg of bone on C2, the dens, sits against the inside of the front arch and is held there by the transverse ligament. This pivot, with two flatter joints at the sides, is what lets you look over your shoulder.

A clinical review describes the atlanto-axial joint as the most mobile joint, with several critical nerves and blood vessels passing through it (Lacy et al., 2023). The atlas’s side projections are long and act as levers for the muscles that rotate the head. Small holes in them, and a groove on the back arch, carry the vertebral artery towards the brain (Kenhub). The rest of the neck is described under cervical spine.

Which muscles attach to the atlas?

Several muscles that desk workers feel are anchored here:

• Two of the four suboccipital muscles run from C1 to the skull and extend the head, and a third runs from C2 to C1 and helps turn it (TeachMeAnatomy).
• The levator scapulae starts on the side projections of C1 to C4 and runs down to the shoulder blade (Kenhub).
• At the front, the longus colli, one of the deep neck flexors, reaches up to the front arch of the atlas (Kenhub).

Why does the top of the neck matter at a screen?

The usual picture of forward head posture is that, as the head drifts ahead of the shoulders, it tips back at the very top of the neck to keep the eyes level with the screen. Evidence for that is mixed. In whole-body X-rays of 201 adults referred for back pain, those with forward head posture did show more extension in the upper neck (Rios-Peralta et al., 2026). An older photographic study of people standing found no relationship between a forward head and upper neck extension (Raine & Twomey, 1994). See forward head posture and the guide to monitor setup.

The upper neck is also linked with headaches. A cervicogenic headache is one-sided pain that starts in the neck and is referred from its bones or soft tissues, often after neck movement and with reduced range of motion (Al Khalili et al., 2022). The suboccipital muscles have been implicated because of their connections with the membrane around the spinal cord (George & Tadi, 2023). The greater occipital nerve and Can neck pain cause headaches? cover this further.

When to see a doctor

A heavy vertical impact on a neck that is bent back, such as diving into water that is too shallow, can fracture it (TeachMeAnatomy). Instability between C1 and C2 is usually present from birth, but in adults it can follow an injury or degenerative disease (Lacy et al., 2023). After any neck injury, get an urgent GP appointment or call 111 if you have severe pain despite painkillers, pins and needles on one or both sides, trouble walking or sitting upright, an electric-shock feeling down the spine, or weak hands, arms or legs (NHS).

For everyday neck pain, see a GP if it hasn’t gone after a few weeks, painkillers haven’t helped, or you have pins and needles or a cold arm (NHS). Call 999 for new problems walking, loss of bladder or bowel control, sudden clumsiness with tasks such as buttoning a shirt, a face that droops on one side, being unable to lift both arms and keep them there, or slurred speech (NHS).