OA Joint Motion
Primary motion is flexion/extension (nodding 50%); SB & R in opposite directions
AA Joint Motion
Pure rotation: provides 50% of total cervical rotation; tested at 45° cervical flexion
C2–C7 Facets
Superior facets face BUM (Back, Up, Medial); SB & R in same direction
Alar Ligament Risk
Dens instability in Rheumatoid Arthritis & Down Syndrome — HVLA strictly contraindicated
Occipitoatlantal (OA) Joint Mechanics
The OA joint is formed by the convex occipital condyles articulating with the concave superior articular facets of the atlas (C1). It acts as a universal pivot for head pitch:
Primary Motion
Flexion and extension (the 'yes' joint). Responsible for approximately 50% of total cervical flexion/extension.
Coupled Motion Rule
Sidebending and rotation ALWAYS occur to OPPOSITE sides, regardless of whether the joint is in flexion, neutral, or extension (e.g., OA F SLRR).
Translation Testing
Translating the occiput to the right induces left sidebending. If right translation is restricted in extension, the occiput is restricted in left sidebending in extension, meaning it is free in right sidebending in flexion (OA F SRRL).
Atlantoaxial (AA) Joint Mechanics
The AA joint is formed by the dens (odontoid process) of C2 articulating with the anterior arch of C1. It is the primary rotation engine of the cervical spine:
Primary Motion
Pure axial rotation. Contributes 50% of total cervical rotation (approximately 45° to each side).
Isolation Testing Technique
To test the AA joint, flex the patient's cervical spine to 45 degrees. This locks the C2–C7 facet joints in the sagittal plane, ensuring all subsequent rotation occurs strictly at the AA joint.
Naming AA Dysfunctions
Named purely for rotational freedom:
AA RR (rotated right) or AA RL (rotated left).Typical Cervical Vertebrae (C2–C7)
Vertebrae C2 through C7 possess uncovertebral joints (joints of Luschka) and distinct facet orientations:
| Level / Landmark | Facet Orientation | Coupling Motion | Clinical Significance |
|---|---|---|---|
| Cervical (C2–C7) | BUM (Back, Up, Medial; 45° angle) | SB and Rotation in SAME direction | Joints of Luschka prone to degenerative osteophytes compressing spinal nerves |
| Thoracic (T1–T12) | BUL (Back, Up, Lateral; 60° angle) | Fryette Law I (Neutral: Opp) or II (Non-neutral: Same) | Rib articulations limit sidebending and flexion; greatest rotation |
| Lumbar (L1–L5) | BM (Back, Medial; 90° angle) | Fryette Law I or II | Sagittal orientation favors flexion/extension; minimal rotation |
Thoracic Outlet Syndrome & Scalene Entrapment
The neurovascular bundle (brachial plexus trunks and subclavian artery) traverses three anatomical bottlenecks in the cervical and thoracic root:
1. Interscalene Triangle
Between anterior scalene, middle scalene, and rib 1. Compresses brachial plexus trunks and subclavian artery. Tested with Adson's Test (extend neck, turn head toward affected side, inhale deeply; positive if radial pulse diminishes).
2. Costoclavicular Space
Between clavicle and rib 1. Tested with Military Posture / Costoclavicular Test (shoulders drawn down and backward).
3. Retropectoralis Minor Space
Underneath pectoralis minor tendon and coracoid process. Tested with Wright's Hyperabduction Test.
COMLEX / OMM Integration
NBOME High-Yield Correlate
Suboccipital Release & Vagal Tone
- Suboccipital Release: Gentle cephalad finger pressure along the inferior nuchal line relaxes the rectus capitis posterior and obliquus capitis muscles.
- Vagal Nerve Stimulation: The vagus nerve (CN X) exits the jugular foramen between the occiput and temporal bone. Decompressing the OA joint and suboccipital musculature relieves entrapment and normalizes parasympathetic output to the heart, lungs, and upper GI tract.
- Vagal Nerve Stimulation: The vagus nerve (CN X) exits the jugular foramen between the occiput and temporal bone. Decompressing the OA joint and suboccipital musculature relieves entrapment and normalizes parasympathetic output to the heart, lungs, and upper GI tract.
Board Traps & Common Distractors
- Absolute Contraindication: Never perform HVLA thrust on C1/C2 (AA joint) in patients with Rheumatoid Arthritis or Down Syndrome due to transverse ligament laxity / dens subluxation risk causing cord compression.
- Vertebral Artery Compromise: Screen with extension and rotation prior to cervical manipulation. Vertebral basilar insufficiency signs (dizziness, diplopia, dysarthria, drop attacks, dysphagia) mandate immediate cessation.