Atlanto-occipital joint: Difference between revisions

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'''Original Editor '''- Your name will be added here if you created the original content for this page.
'''Original Editor''' - [[User:Rachael Lowe|Rachael Lowe]]


'''Lead Editors''' &nbsp;
'''Lead Editors''' - [[User:Evan Thomas|Evan Thomas]]
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== Description  ==
== Description  ==


[[Image:Atlanto-occipital joint anterior.png|thumb|right|Atlanto-occipital joint (anterior)]][[Image:Atlanto-occipital_joint_posterior.png|thumb|right|Atlanto-occipital joint (posterior)]]The atlanto-occipital articulations function as bilaterally symmetrical condyloid synovial joints. &nbsp;
[[Image:Atlanto-occipital joint anterior.png|thumb|right|Atlanto-occipital joint (anterior)]][[Image:Atlanto-occipital joint posterior.png|thumb|right|Atlanto-occipital joint (posterior)]]The atlanto-occipital articulations function as bilaterally symmetrical ellipsoid synovial joints between C0 and C1.  


== Articulating Surfaces  ==
== Articulating Surfaces  ==
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Occipital condyles and a superior articular facets of the atlas.  
Occipital condyles and a superior articular facets of the atlas.  


== Ligaments &amp; Joint Capsule<br>  ==
== Ligaments &amp; Joint Capsule   ==


The capsule is rather roomy and relaxed and the joint possesses no individual accessory ligaments:<br>  
The capsule is rather roomy and relaxed and the joint possesses no individual accessory ligaments. &nbsp;Stability is provided by:<br>  


*Two articular capsules  
*Two articular capsules  
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*[[Anterior atlanto-occipital ligament]]
*[[Anterior atlanto-occipital ligament]]


== Muscles ==
== Degrees of Freedom ==


== Motions Available  ==
Two degrees of freedom are available at this joint:<ref name="Ortho Div CPA">Orthopaedic Division of the Canadian Physiotherapy Association. Biomechanics of the Atlanto-Occipital Joint. Clinical Technique Manual: Level II Upper Quadrant (2010). Pg 28-30.</ref>


The movements permitted in this joint are: (a) flexion and extension around the mediolateral axis, which give rise to the ordinary forward and backward nodding of the head. (b) slight lateral motion, lateroflexion, to one or other side around the anteroposterior axis.
#Flexion/extension
#Lateral flexion/conjunct rotation


Flexion is produced mainly by the action of the longi capitis and recti capitis anteriores; extension by the recti capitis posteriores major and minor, the obliquus capitis superior, the semispinalis capitis, splenius capitis, sternocleidomastoideus, and upper fibers of the trapezius.
== Osteokinematics<ref name="Ortho Div CPA" />  ==


The recti laterales are concerned in the lateral movement, assisted by the trapezius, splenius capitis, semispinalis capitis, and the sternocleidomastoideus of the same side, all acting together.
*Flexion/extension
**Cardinal (pure) swing
**Total ROM: 30° (10° flexion, 20° extension)
**Axis: Transverse axis through external auditory meatus


<br>
*Lateral flexion
**Arcuate (impure) swing with coronal conjunct rotation (e.g. right lateral flexion occurs with conjunct left rotation)
**Total ROM: 15° (8-10° in each direction)
**Axis: Oblique sagittal axis through the nose (approximately)
**Associated with AA joint rotation


== Closed Packed Position  ==
*Rotation (conjunct)
**Occurs with lateral flexion due to the slanted articular surfaces, anteromedial orientation of the articular facets, and the alar ligaments
**Total ROM: 5-7° in each direction
**Axis: Vertical axis anterior to the foramen magnum


== Open Packed Position ==
== Arthrokinemtics<ref name="Ortho Div CPA" /> ==


== Other Important Information ==
*Flexion
**Forward tilt/nod of the head
**Posterior glide of the convex occipital condyles on the concave atlantal facets
**Atlas moves anterior and cranially
**Dens follows atlas and approaches the clivus
**Occiput and the posterior atlantal arch separate
 
*Extension
**Backward tilt of the head
**Anterior glide of the convex occipital condyles on the concave atlantal facets
 
*Lateral flexion (left lateral flexion example provided below)
**Left lateral tilt of the head causes a contralateral glide of the occiput
**Conjunct right rotation occurs due to the anteriormedial axis of the joint surfaces
**Right glide of the occipital condyles causes relative anterior glide of the left condyle on and a relative posterior glide of the right condyle
**Occipital portion of the right alar ligament tightens, with the left being slackened
**Tension in the right alar ligament pulls on the dens and causes a left rotation of the axis
**Spinous process of the axis moves to the right creating a relative right rotation of the AA joint
 
== Muscle Action at this Joint ==
 
'''Flexion''' is produced mainly by the action of the rectus capitis anterior. Limited by tectoral membrane.
 
'''Extension''' by the rectus capitis posterior major and minor, assisted by the obliqus capitis superior, the semispinalis capitis, splenius capitis, sternocleidomastoid, and upper fibers of the trapezius.
 
The rectus capitis lateralis are concerned in the '''lateral flexion''', assisted by the trapezius, splenius capitis, semispinalis capitis, and the sternocleidomastoid of the same side, all acting together.
 
== Pathology  ==
 
*[[Jefferson fracture|Jefferson fracture]]
*Atlanto-occiptal dislocation


== Resources  ==
== Resources  ==


== Recent Related Research (from [http://www.ncbi.nlm.nih.gov/pubmed/ Pubmed])  ==
*[https://www.youtube.com/watch?v=Ocp5XGW3z4k Flexion/extention motion at the AO joint (YouTube)]
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== References  ==
== References  ==


References will automatically be added here, see [[Adding References|adding references tutorial]].
<references />


<references />
[[Category:Cervical Spine - Anatomy]]
[[Category:Joints]]
[[Category:Cervical Spine - Joints]]
[[Category:Cervical Spine]]

Latest revision as of 13:40, 23 August 2019

Original Editor - Rachael Lowe

Lead Editors - Evan Thomas

Description[edit | edit source]

Atlanto-occipital joint (anterior)
Atlanto-occipital joint (posterior)

The atlanto-occipital articulations function as bilaterally symmetrical ellipsoid synovial joints between C0 and C1.

Articulating Surfaces[edit | edit source]

Occipital condyles and a superior articular facets of the atlas.

Ligaments & Joint Capsule[edit | edit source]

The capsule is rather roomy and relaxed and the joint possesses no individual accessory ligaments.  Stability is provided by:

Degrees of Freedom[edit | edit source]

Two degrees of freedom are available at this joint:[1]

  1. Flexion/extension
  2. Lateral flexion/conjunct rotation

Osteokinematics[1][edit | edit source]

  • Flexion/extension
    • Cardinal (pure) swing
    • Total ROM: 30° (10° flexion, 20° extension)
    • Axis: Transverse axis through external auditory meatus
  • Lateral flexion
    • Arcuate (impure) swing with coronal conjunct rotation (e.g. right lateral flexion occurs with conjunct left rotation)
    • Total ROM: 15° (8-10° in each direction)
    • Axis: Oblique sagittal axis through the nose (approximately)
    • Associated with AA joint rotation
  • Rotation (conjunct)
    • Occurs with lateral flexion due to the slanted articular surfaces, anteromedial orientation of the articular facets, and the alar ligaments
    • Total ROM: 5-7° in each direction
    • Axis: Vertical axis anterior to the foramen magnum

Arthrokinemtics[1][edit | edit source]

  • Flexion
    • Forward tilt/nod of the head
    • Posterior glide of the convex occipital condyles on the concave atlantal facets
    • Atlas moves anterior and cranially
    • Dens follows atlas and approaches the clivus
    • Occiput and the posterior atlantal arch separate
  • Extension
    • Backward tilt of the head
    • Anterior glide of the convex occipital condyles on the concave atlantal facets
  • Lateral flexion (left lateral flexion example provided below)
    • Left lateral tilt of the head causes a contralateral glide of the occiput
    • Conjunct right rotation occurs due to the anteriormedial axis of the joint surfaces
    • Right glide of the occipital condyles causes relative anterior glide of the left condyle on and a relative posterior glide of the right condyle
    • Occipital portion of the right alar ligament tightens, with the left being slackened
    • Tension in the right alar ligament pulls on the dens and causes a left rotation of the axis
    • Spinous process of the axis moves to the right creating a relative right rotation of the AA joint

Muscle Action at this Joint[edit | edit source]

Flexion is produced mainly by the action of the rectus capitis anterior. Limited by tectoral membrane.

Extension by the rectus capitis posterior major and minor, assisted by the obliqus capitis superior, the semispinalis capitis, splenius capitis, sternocleidomastoid, and upper fibers of the trapezius.

The rectus capitis lateralis are concerned in the lateral flexion, assisted by the trapezius, splenius capitis, semispinalis capitis, and the sternocleidomastoid of the same side, all acting together.

Pathology[edit | edit source]

Resources[edit | edit source]

References[edit | edit source]

  1. ↑ 1.0 1.1 1.2 Orthopaedic Division of the Canadian Physiotherapy Association. Biomechanics of the Atlanto-Occipital Joint. Clinical Technique Manual: Level II Upper Quadrant (2010). Pg 28-30.
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