When I was studying my physiotherapy degree, I could count a million times I heard "look at the anatomy..."
"The anatomy of the high cervical spine is unique and, to some degree, more complicated to assess than the rest of the vertebral column. The shape of the bones and their articulations are distinctly different between the occiput and atlas, atlas and axis, and axis and C3. Such a marked change in anatomy does not occur in such close proximity anywhere else in the vertebral column" (Edwards, 1992, pp. 42-43). Due to the close proximity of this region of the spine, careful consideration must be made when understanding which level is being loaded under pressure, and what sensitising movements can be applied to differentiate between intra-articular and periarticular restrictions to movement. Each of these joints have distinguishing features which contribute to their function.
The atlanto-occipital joint O-C1
The atlas is a ringlike kidney-shaped bone which has anterior and posterior arches and doesn’t have a spinous process. The O-C1 joint or atlanto-occipital joint is located between the superior concave sockets of the atlas (C1) and the occipital condyles of the skull. It is a very stable joint due to the design of the articular surfaces and provides stability for the transfer of weight from head to neck and to balance the head on the neck.
The O-C1 joint is often thought of the main contributor to upper cervical flexion/extension and functionally assessed with nodding movements. The deep walls of each articular facet prevent translation movements of the head laterally, posteriorly, and anteriorly, but they do permit nodding. Flexion/extension is the primary movement of the O-C1 joint. Studies vary but the average range is 0-25 degrees of total movement with more extension than flexion (Oatis, 2004).
The Atlanto-axial joint C1-C2
The axis (C2) is a completely different shape with a peg-like dens (odontoid process) which projects superiorly from the vertebral body. The dens is stabilised by a strong transverse ligament which extends between the tubercles on the medial aspects of the lateral masses of the C1 vertebrae and holds the dens agains the anterior arch of C1. The axis also has a long (and often bifid) spinous process and each of the transverse processes have anterior and posterior tubercles for muscular attachment.
The C1/C2 (or AA) joint functions as a place for multiple muscular attachment sites (think rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis superior and obliquus capitis inferior.
It also acts in transmitting forces and load through the cervical spine.
It is the joint that provides a large proportion of axial rotation of the head i.e. 45-57 degrees. The AA joint contributes 50% of overall cervical rotation. There are also small amounts of flexion, extension and lateral flexion.
Due to the shape of the facet joints and their oblique orientation, pure AP translation does not occur. Instead it is coupled by superior and inferior movements which allow the occiput and atlas to roll on the axis.
Clinical relevance - cervicogenic headache
In regards to the cervical spine and cervicogenic headaches (CGH), my approach follows the work of Specialist Physiotherapists Dean Watson and Gwen Jull. Mr Watson is renowned for his approach to palpation of the upper cervical spine in the diagnosis and management of cervicogenic headaches and Gwen Jull has been involved in many of the leading research papers for motor control dysfunction and treatment for whiplash disorders and neck pain.
Currently three musculoskeletal impairments have been validated as clinical features of CGH (Jull, Amiri, Bullock‐Saxton, Darnell, & Lander, 2007; King, Lau, Lees, & Bogduk, 2007; Zito, et al., 2006):
A painful upper cervical joint,
Loss of range of movement, and
Impairment in the muscular system of the cervical spine.
There are two cardinal signs of CGH, which to this day remain vital features in differential diagnosis. These are the presence of a unilateral headache and the provocation of headache with neck movements. The current definition is presented in Jull, Sterling, Falla, Treleaven, and O'Leary (2009, p. 119). One important and often under described component of the physical examination is the manual palpation of the upper cervical spine. Maitland and Hengeveld (2005) describe manual palpation as an objective way to measure the range and quality of movement at a spinal segment. Accuracy and sensitivity of palpation relies on the therapist' ability to describe the end-feel of a joint, the quality of resistance through movement and the reproduction of pain.
Palpation tips for the upper cervical spine
Edwards (1992) and Maitland (2005) recommend that palpation of the upper cervical spine should be used to confirm the findings of the active range of movement and passive physiological range of movement assessment. They also suggests that palpation should be combined with movements to enhance structural differentiation. Below is an example of this structural differentiation.
"There is another particularly important test procedure that is used when it is necessary to determine whether a patient's symptoms arise from a disorder of the C2-3 apophyseal joint or the C1-2 apophyseal joint. With the patient prone and the head in the neutral position, poster-anterior pressures are applied, for example, to the left articular pillar of C2 so as to move it in a poster-anterior direction. The quality and range of movement, and the accompanying pain response, are compared with the same features when the postero-anterior pressure is applied with the same strength to C2, but this time with the patient's head rotated approximately 30-40 degrees to the left. If the pain response is greater with the head rotated than it is with the head straight, the disorder is at the C1-2 joint. If the pain response is greater with the head straight, then the disorder is at the C2-3 joint." (Maitland., 2005, p. 259).
Founder of the Watson Headache Clinic and Institute, Dean Watson, has presented a similar framework. Watson's primary objective is the reproduction and reduction of the patient's headache, and his clinical experience provides an un-published, yet logical and consistent method for manual examination of the upper cervical spine. Watson describes a similar process to Edwards and Maitland, using sensitizing movements such as upper cervical flexion, ipsilateral and contralateral rotation, and cephalad/caudad/transverse inclinations on the specified level to assist localization of a symptomatic level and with headache reproduction.
Below is how I think about structural differentiation of palpation of the upper cervical spine:
Posterior-anterior (PA) pressure on left C1 with the head in right rotation and flexion increases stretch at C1/2 joint.
PA pressure on left C2 in right rotation and flexion decreases stretch at C1/2 joint.
PA pressure on left C2 with head in left rotation and extension increases stretch at C1/2 joint.
PA pressure on left C1 with head in left rotation and extension decreases rotation at C1/2 joint.
A few additional points to add to the structural differentiation above are (Edwards, 1992):
In extension and contralateral rotation:
AP on the C1 increases stress at the O-C1 joint but decreases stress on the C1-2 joint
AP on the C2 increases stress at the C1-2 joint
PA on the C1 decreases stress at O-C1 joint
In flexion and ipsilateral rotation
AP on C1 decreases stress at O-C1 joint
PA on C1 decreases stress at C1-2 joint
PA on C2 increases stress at C1-2 joint
In flexion and contralateral rotation
AP on C2 increases stress at C1-2 joint
AP on C1 decreases stress at C1-2 joint
PA on C1 increases stress at C1-2 joint
Once you have identified the joint which you wish to treat i.e. O-C1, C1-C2, C2-C3 and decided if the joint has an issue with opening or closing based on your palpation findings, you can select a treatment that you are both comfortable with, proficient at performing, and will address these treatment findings. This might include a joint mobilisation (PAIVM or PPIVM), joint high velocity thrust, muscle energy techniques (MET), active release therapy (ART) or soft tissue massage (STM)….. there are many options to choose from.
Blogs previously written on the cervical spine
Cervical Motor Control
Edwards, B. C. (1992). Manual of combined movements: their use in the examination and treatment of mechanical vertebral column disorders: Churchill Livingstone.
Jull, G., Amiri, M., Bullock-Saxton, J., Darnell, R., & Lander, C. (2007). Cervical musculoskeletal impairment in frequent intermittent headache. Part 1: Subjects with single headaches. Cephalalgia, 27(7), 793-802.
Jull, G., Sterling, M., Falla, F., Treleaven, J., & O'Leary, S. (2009). Whiplash, headache and neck pain. Edinburgh: Elsevier Churchill-Livingstone.
King, W., Lau, P., Lees, R., & Bogduk, N. (2007). The validity of manual examination in assessing patients with neck pain. The Spine Journal, 7(1), 22-26.
Maitland, G. D., & Hengeveld, E. (2005). Maitland's vertebral manipulation. Edinburg: Elsevier Butterworth-Heinemann.
Watson, D. (2008). The role of Co-C3 Segmental Dysfunction in Primary Headache.Unpublished manuscript, Murdoch university, WA.
Zito, G., Jull, G., & Story, I. (2006). Clinical tests of musculoskeletal dysfunction in the diagnosis of cervicogenic headache. Manual therapy, 11(2), 118-129.