Rectus Capitis Posterior Major: Origin, Insertion, Nerve & Dural Bridges

The Rectus Capitis Posterior Major (RCPM) is the larger of the two "posterior straight" muscles in the suboccipital triangle. Located deep at the base of the skull, it is a primary fine-tuner of head position and has a controversial but critical anatomical link to the dura mater (brain covering).

[Image of Longissimus Capitis anatomy]

Quick Anatomy Snapshot

Group	Suboccipital Muscles (Deep Neck).
Origin (Proximal)	Spinous Process of the Axis (C2).
Insertion (Distal)	Lateral part of the Inferior Nuchal Line of the Occipital Bone.
Nerve Supply	Suboccipital Nerve (Posterior Ramus of C1).
Primary Actions	Bilateral: Extension of the head at the Atlanto-Occipital joint. Unilateral: Rotation of the head to the same side (Ipsilateral).

Deep Dive: The Triangle Boundary

The Suboccipital Triangle is a famous anatomical landmark. The Rectus Capitis Posterior Major forms the Superomedial border of this triangle.

1. The C2-to-Skull Connection

While its smaller partner (Rectus Capitis Posterior Minor) goes from C1 to the skull, the Major goes from C2 (Axis) to the skull. This diagonal path allows it to create rotation at the C1-C2 joint, which accounts for 50% of all cervical rotation.

2. The Myodural Bridge

Recent research has confirmed that connective tissue bridges ("Myodural Bridges") connect the fascia of the Rectus Capitis Posterior Major directly to the Spinal Dura Mater (the protective covering of the spinal cord). This suggests that tension in this muscle can physically pull on the sensitive dura, potentially causing cervicogenic headaches.

Physio Corner: Clinical Relevance

💪 Functional Fact: The suboccipital muscles have the highest density of muscle spindles (sensors) in the body per gram of muscle. They act as "proprioceptive monitors," constantly telling your brain where your head is to keep your eyes level.

Palpation

Caution: This area is sensitive.
Locate the spinous process of C2 (the first palpable bump below the skull). Move slightly superior and lateral. The muscle lies deep to the Trapezius and Semispinalis Capitis. Palpation feels like deep, dense tissue at the base of the skull.

⚠️ Clinical Pathology: Tension Headaches
Chronic forward head posture ("Text Neck") keeps the suboccipitals in a shortened, tight state. This can compress the Greater Occipital Nerve (which loops under the Obliquus Capitis Inferior nearby) or pull on the dura via the myodural bridge, causing headaches that wrap over the head to the eye.

Functional Testing

Specific isolation is impossible, but we assess the suboccipital group via upper cervical extension.

Testing Tip: Watch for the "Chin Poke." If a patient tries to look up but juts their chin forward excessively, it indicates dominance of the suboccipital extensors over the deep neck flexors.

Step-by-Step Procedure (Upper Cervical Extension)

Test	Patient Action & Observation
Craniocervical Extension	Position: Prone, head off table. Action: Patient tips the head back (looks at wall) without extending the lower neck. Resistance: Applied gently to the occiput. Result: Pain or inability to hold the position without recruiting superficial muscles indicates dysfunction.

Frequently Asked Questions

What is the difference between Major and Minor?

Major: Originates on C2 (Axis), inserts laterally on nuchal line. Rotates and extends.
Minor: Originates on C1 (Atlas), inserts medially on nuchal line. Only extends (no rotation).

Does it rotate the head to the opposite side?

No. Because it runs obliquely from the midline (C2) outward to the skull, when it shortens, it turns the face to the Same Side (Ipsilateral).

What nerve passes through the Suboccipital Triangle?

The Suboccipital Nerve (C1 dorsal ramus) supplies the muscles of the triangle. The Vertebral Artery also passes deep within this triangle.

Test Your Knowledge: Rectus Capitis Posterior Major Quiz

1. What is the origin of the Rectus Capitis Posterior Major?

2. Which nerve supplies this muscle?

3. The RCPM forms which border of the Suboccipital Triangle?

4. What is the unilateral action of the RCPM?

5. The "Myodural Bridge" connects the RCPM fascia to the:

6. Where does the RCPM insert?

7. The suboccipital muscles have a high density of:

8. Which muscle lies medial to the Rectus Capitis Posterior Major?

9. What vessel passes deep to the suboccipital triangle?

10. True or False: The RCPM is visible superficially on the back of the neck.

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer.
• Standring, S. (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier.
• Hack, G. D., et al. (1995). Anatomic relation between the spinal dura mater and the suboccipital musculature. Spine.