Classification
- Type: Synovial condyloid (biaxial)
- Degrees of freedom: 2 (flexion/extension as primary; slight lateral flexion)
- Region: Upper cervical spine (craniocervical junction, along with the anatomy/joints/atlantoaxial joint)
Articular Surfaces
- Occipital condyles (convex): Two oval, convex prominences on the inferior surface of the occipital bone, flanking the foramen magnum. They are oriented obliquely — converging anteriorly — which inherently limits rotation. Covered with hyaline cartilage.
- Superior articular facets of C1 (concave): Two kidney-shaped, concave facets on the lateral masses of the atlas. They face superiorly and slightly medially, cradling the occipital condyles. The concave shape allows the rocking (flexion/extension) motion characteristic of this joint.
Movements and ROM
| Movement |
Normal ROM |
Plane |
Muscles Producing |
| Flexion |
5–10° |
Sagittal |
anatomy/muscles/longus-capitis, anatomy/muscles/rectus-capitis-anterior |
| Extension |
10–15° |
Sagittal |
anatomy/muscles/rectus-capitis-posterior-major, anatomy/muscles/rectus-capitis-posterior-minor, anatomy/muscles/obliquus-capitis-superior, anatomy/muscles/semispinalis-capitis, anatomy/muscles/splenius-capitis, anatomy/muscles/upper-trapezius |
| Lateral flexion |
5° (each side) |
Frontal |
anatomy/muscles/rectus-capitis-lateralis, anatomy/muscles/obliquus-capitis-superior, anatomy/muscles/sternocleidomastoid |
| Rotation |
Minimal (1–2°) |
Transverse |
Virtually no rotation — the oblique orientation of the condyles prevents it |
The "yes" joint. Flexion/extension (nodding) is the primary motion at C0-C1. Rotation ("no" movement) occurs almost entirely at the anatomy/joints/atlantoaxial joint. This distinction is essential for localizing upper cervical dysfunction during assessment.
Capsular Pattern
Extension > Lateral flexion (equal bilaterally)
The capsular pattern is debated and less clearly defined than peripheral joint patterns. Restriction at C0-C1 primarily limits extension and, to a lesser degree, lateral flexion. Some sources describe the pattern as extension limitation predominating.
Resting Position
- Neutral (midway between flexion and extension)
Close-Packed Position
- Full extension
- Maximum bony congruence, capsule and ligaments taut
End-Feels
| Movement |
Normal End-Feel |
Type |
| Flexion |
Capsular (firm) |
Posterior capsule, ligamentum nuchae, posterior suboccipital muscles |
| Extension |
Capsular (firm) / bony |
Anterior capsule; may be bony as the posterior arch of C1 contacts the occiput |
| Lateral flexion |
Capsular (firm) |
Contralateral capsule and alar ligament |
Ligaments
Anterior Atlantooccipital Membrane
- Attachments: Anterior arch of C1 → anterior margin of the foramen magnum
- Function: Resists extension. Continuous with the anterior longitudinal ligament inferiorly.
Posterior Atlantooccipital Membrane
- Attachments: Posterior arch of C1 → posterior margin of the foramen magnum
- Function: Resists flexion. The vertebral artery pierces this membrane laterally before entering the foramen magnum — this is a site of potential vertebral artery compression.
Alar Ligaments
- Attachments: Lateral aspect of the dens of C2 → medial aspect of the occipital condyles (and lateral masses of C1)
- Function: Check ligaments that limit rotation and lateral flexion. The alar ligaments are the primary restraints against excessive rotation — they prevent the head from rotating too far on the atlas and axis. Disruption (from trauma, RA, Down syndrome) creates craniocervical instability — a potentially life-threatening condition.
- Assessment test: Alar ligament stress test — rotation of the skull should produce immediate coupled lateral flexion of C2. If C2 does not move, the alar ligaments may be disrupted. This test requires considerable skill.
- Condition link: Craniocervical instability, atlantoaxial instability
Tectorial Membrane
- Attachments: Posterior body of C2 → anterior margin of the foramen magnum (internal surface of the occipital bone)
- Function: The continuation of the posterior longitudinal ligament into the cranium. Resists excessive flexion and vertical translation of the dens. A critical stabilizer of the craniocervical junction.
Mobilization Techniques
Hands-on instruction is required. The descriptions below provide clinical reference detail for understanding and supervised practice. They are not a substitute for instructor-led technique training. Correct hand placement, force dosage, and tissue response interpretation require hands-on coaching and feedback.
Convex-Concave Rule at the Atlantooccipital Joint
The occipital condyles are
convex moving on the
concave atlas facets. The glide occurs in the
opposite direction to the restricted movement (convex on concave).
| Restricted Movement |
Glide Direction |
Reasoning |
| Flexion |
Posterior glide of occiput |
Flexion rolls the condyles anteriorly → convex on concave → glide opposite → posterior |
| Extension |
Anterior glide of occiput |
Extension rolls the condyles posteriorly → convex on concave → glide opposite → anterior |
General Contraindications (All Craniocervical Mobilizations)
- Absolute: Craniocervical instability (Down syndrome, RA with pannus eroding the transverse ligament, post-trauma with suspected alar or transverse ligament disruption), vertebral artery insufficiency (positive VBI screening), basilar invagination, Arnold-Chiari malformation, acute fracture (C1 Jefferson fracture, C2 odontoid fracture), cervical myelopathy signs (upper motor neuron signs, clonus, Babinski), active infection
- Relative: Osteoporosis (Grade I–II only with extreme caution), advanced degenerative changes, anticoagulant therapy, elderly patients (vertebral arteries are more vulnerable)
- VBI screening is mandatory. Before any upper cervical mobilization, perform vertebral artery screening: sustained cervical extension, rotation, and combined positions. Positive signs (dizziness, nystagmus, visual disturbance, nausea, dysarthria) are absolute contraindications.
Posterior Occipital Glide (Nodding Flexion)
Purpose: Restores flexion at C0-C1. Stretches the posterior suboccipital muscles and posterior capsule. Useful for headache patients with restricted upper cervical flexion.
Patient position:
- Supine on the treatment table
- Head cradled in the clinician's hands, supported off the edge of the table or on a pillow
- Cervical spine in neutral — no rotation, no lateral flexion
Hand placement:
- Stabilizing hand/contact: The clinician's fingertips of both hands cradle the occiput, with the fingers resting in the suboccipital space (between the occiput and the posterior arch of C1). The fingertips contact the occiput itself, not C1.
- Alternative: One hand cradles the occiput; the other hand gently stabilizes the forehead to control the direction of motion.
Technique execution:
- Produce a gentle nodding motion — anterior tipping of the skull on C1, which produces a posterior glide of the occipital condyles on the atlas facets
- Grade I–II: Gentle, small amplitude nodding oscillations. The motion should be a pure nod — no cervical flexion (chin tucking without lower cervical movement).
- Grade III: Sustained nod at end-range for capsular stretch. Extremely gentle — this is a small joint with critical structures nearby.
- Duration: 15–30 seconds per set, 2–3 sets
- The total excursion is very small (5–10° total) — do not force
Indications:
- Restricted upper cervical flexion (cannot fully nod chin toward chest without compensating with lower cervical flexion)
- Cervicogenic headache with suboccipital tension (the suboccipital muscles are primary headache generators when hypertonic)
- Forward head posture rehabilitation — restoring upper cervical flexion is the first step in correcting forward head posture
Technique notes:
- Common error: Flexing the entire cervical spine instead of isolating C0-C1 nodding. The lower cervical spine must remain neutral.
- Common error: Excessive force — the upper cervical spine requires very little force for mobilization.
- Reassessment: Re-test active chin nod (cranio-cervical flexion test). Improvement in range and quality of the nod confirms C0-C1 involvement.
- Integration: Perform after suboccipital muscle release (RCPma, RCPmi, OCS, OCI). Release the suboccipitals first, then mobilize the joint — this sequence is far more effective than either alone.
Lateral Glide (for Lateral Flexion)
Purpose: Restores lateral flexion at C0-C1. Useful when one side is restricted (common in cervicogenic headache with unilateral symptoms).
Patient position:
- Supine, head cradled in the clinician's hands
Hand placement:
- Both hands cradle the occiput. The clinician's fingertips are positioned at the level of the C0-C1 joint. The hand on the restricted side provides the mobilizing force.
Technique execution:
- Apply a gentle translatory force directed laterally — gliding the occiput on the atlas toward the unrestricted side (this gaps the restricted side)
- Grade I–II: Small oscillations for pain modulation
- Grade III: Gentle oscillations into the end-range lateral resistance
- Duration: 15–30 seconds per set, 2–3 sets
Indications:
- Asymmetric lateral flexion restriction at C0-C1
- Unilateral cervicogenic headache with ipsilateral C0-C1 restriction
- Torticollis with upper cervical involvement
Technique notes:
- Palpation before mobilizing: Palpate the C1 transverse process (the widest cervical transverse process, palpable between the mastoid process and the angle of the mandible) to assess C0-C1 position and mobility.
- Do not combine with rotation. Rotation at C0-C1 is minimal by design. Adding rotation during mobilization risks vertebral artery compression.
Muscles Crossing This Joint
Suboccipital Muscles (the four deep extensors)
- anatomy/muscles/rectus-capitis-posterior-major — extends and rotates the head; from C2 spinous process to the occiput
- anatomy/muscles/rectus-capitis-posterior-minor — extends the head; from C1 posterior tubercle to the occiput; connected to the spinal dura via the myodural bridge
- anatomy/muscles/obliquus-capitis-superior — extends and laterally flexes the head; from C1 transverse process to the occiput
- anatomy/muscles/obliquus-capitis-inferior — rotates C1 on C2 (not a C0-C1 muscle but functionally linked to suboccipital mechanics)
Superficial Muscles Acting on C0-C1
- anatomy/muscles/sternocleidomastoid — bilaterally: flexes the head on the neck; unilaterally: rotates and laterally flexes
- anatomy/muscles/upper-trapezius — extends the head; inserts on the superior nuchal line
- anatomy/muscles/splenius-capitis — extends, rotates, and laterally flexes the head
- anatomy/muscles/semispinalis-capitis — the most powerful head extensor; inserts on the occiput between the nuchal lines
Conditions Affecting This Joint
- Cervicogenic headache — suboccipital muscle hypertonia and C0-C1/C1-C2 joint dysfunction are primary drivers; headache typically unilateral, starting at the occiput and radiating to the forehead/eye
- conditions/osteoarthritis — C0-C1 OA can restrict nodding and contribute to upper cervical stiffness
- Craniocervical instability — disruption of the alar or transverse ligaments (trauma, RA, Down syndrome); presents with neck pain, dizziness, visual disturbance; requires immediate referral
- Forward head posture — chronic C0-C1 extension (chin poke position) shortens the suboccipital muscles and restricts flexion
Clinical Notes
- Cervicogenic headache is the most common reason to mobilize C0-C1. The suboccipital muscles have the highest density of proprioceptors of any muscles in the body and are intimately connected to the trigeminocervical nucleus — the convergence point for cervical and trigeminal pain pathways. Dysfunction at C0-C1 can produce referred pain throughout the trigeminal distribution (forehead, eye, temple).
- The myodural bridge. Rectus capitis posterior minor has a direct fascial connection to the spinal dura mater. This anatomical link may explain how suboccipital tension produces headache — traction on the dura via the myodural bridge can produce nociceptive input interpreted as headache.
- VBI screening is non-negotiable. The vertebral arteries pass through the transverse foramina of C1 and C2, then pierce the posterior atlantooccipital membrane before entering the skull. Any upper cervical technique that combines extension and rotation can compress the vertebral artery. Screen before every treatment session — VBI status can change between visits.
- Forward head posture creates chronic C0-C1 extension. To keep the eyes level, the head extends on C1 (chin poke). This chronically shortens the suboccipitals and compresses the posterior C0-C1 joint. Restoring C0-C1 flexion (the nod) is the first step in correcting forward head posture.
Key Takeaways
- C0-C1 is the "yes" (nodding) joint — flexion/extension is the primary motion; rotation occurs almost entirely at the anatomy/joints/atlantoaxial joint.
- VBI screening is mandatory before any upper cervical mobilization — the vertebral arteries are vulnerable in this region.
- The suboccipital muscles are primary cervicogenic headache generators — their proprioceptive density and myodural bridge connection explain how C0-C1 dysfunction produces headache.
- Restore C0-C1 flexion (the nod) as the first step in forward head posture correction.
