The atlas posterior motion affects which joint unit?

The atlas posterior motion affects which joint unit?

• A. C0-C1
• B. C2-C3
• C. C1-C2
• D. C3-C4

Answer: (C)

The movement of the atlas (C1) in the back (posterior) mainly involves the joint between the atlas and the axis (C1-C2). The first cervical vertebra sits on top of the second (the axis), and the dens of C2 acts as a pivot for rotation. When the atlas moves posteriorly, that rotary motion is carried through the atlantoaxial joint, making it the joint unit most affected. The joint between the skull and atlas (C0-C1) primarily handles nodding, not the posterior movement of C1, and the C2-C3 or C3-C4 joints are lower in the neck and not the primary site of atlas posterior motion.

The movement of the atlas (C1) in the back (posterior) mainly involves the joint between the atlas and the axis (C1-C2). The first cervical vertebra sits on top of the second (the axis), and the dens of C2 acts as a pivot for rotation. When the atlas moves posteriorly, that rotary motion is carried through the atlantoaxial joint, making it the joint unit most affected. The joint between the skull and atlas (C0-C1) primarily handles nodding, not the posterior movement of C1, and the C2-C3 or C3-C4 joints are lower in the neck and not the primary site of atlas posterior motion.