The rectus capitis lateralis consists of a paired muscle set in the upper neck below the back of the head on each side. They are responsible for controlling movements when the head tilts to either side. This motion is also known as “lateral flexion.”

One end of the muscle attaches to the transverse process at the side of the C1 vertebra (the topmost vertebra of the spinal column), and then travels up to the base of the skull. The other end of the muscle attaches to the jugular process on the lower part of the cranium, an area of bone that sticks out near where the spinal column attaches to the skull.

The anterior primary rami of C1 and C2 provide the nerve supply to the muscle. The cervical artery brings oxygenated blood to the muscle. 

If the C1 vertebra is out of alignment or the neck is tender in that area, a medical examination is advised. Gentle palpation and a range-of-motion check on the area is usually enough to diagnose muscle strain. Palpation is a process where a medical professional uses her or his hands to feel and examine the body. It's unlikely the doctor will locate the muscle directly, but surrounding tissue will exert pressure against the rectus capitis lateralis muscle, alerting the patient to pain. Pain related to this muscle generally occurs deep in the neck tissue just below the base of the skull.