Joints of the vertebral column

Definitions & Key takeaways

Joints of the vertebral column lie between individual vertebrae that make up the spine. Between adjacent vertebrae lie fibrocartilaginous intervertebral discs, which absorb shock and allow movement. Joints of the vertebral column are craniovertebral joints, joints between the vertebral bodies, joints of the vertebral arches (also known as zygapophyseal joints, costovertebral joints, and the sacroiliac joints.

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Introduction0:00–0:23

The joints of the vertebral column include the joints of the vertebral bodies, the joints of the vertebral arches, the craniovertebral joints, costovertebral joints, and the sacroiliac joints.
These joints bear the body weight when sitting or standing, and give us the flexibility to do the downward dog in yoga class.
Let’s start with the joints of the vertebral bodies, which are symphyses or secondary cartilaginous joints - that aid in weight-bearing and provide strength to the vertebral column.

Joints of the vertebral bodies0:23–3:39

The articulating surfaces of adjacent vertebral bodies attach to each other by fibrocartilaginous discs called intervertebral discs or IV discs for short, in addition to numerous ligaments.
The intervertebral discs function as shock absorbers between adjacent vertebrae. They also allow for limited movement between adjacent vertebrae, and while the movement between any two vertebrae is minor, the summation of those limited movements throughout the entirety of the vertebral column allow for the large movements of our spine.
The intervertebral discs consist of two distinct parts, a thick, tough, fibrous outer ring called the anulus fibrosus and a soft gelatinous core called the nucleus pulposus which the anulus fibrosus surrounds.
The anulus fibrosus is made up of circular layers of fibrocartilage, which allows the discs to withstand compression. Now, the nucleus pulposus provides both flexibility and resilience to the intervertebral discs, where the gelatinous core allows the discs to absorb shock when they’re compressed by vertical forces.
The nucleus pulposus is avascular, receiving blood via diffusion from vessels at the periphery of the anulus fibrosus and vertebral body.Now, intervertebral discs are named based on the two vertebrae they lie between.
For example, the C2-C3 disc is the disc between the C2 and C3 vertebral bodies.There are 23 intervertebral discs, starting from the C2-C3 disc all the way down to the L5-S1 disc.
In case you’re wondering, the reason why there’s no disc between C1 and C2 is that these two vertebrae form a different type of joint, called the atlanto-axial joint.
Typically, the thickness of the discs increases as you go down the vertebral column.Now, there are two key ligaments that help maintain the joints of the vertebral bodies: the anterior longitudinal ligament and the posterior longitudinal ligament.
The anterior longitudinal ligament is a strong, wide, fibrous band that runs down the anterior aspects of the vertebral bodies and intervertebral discs.
The ligament extends from the base of the occipital bone and the C1 vertebra to the sacrum. Its main role is to prevent hyperextension of the vertebral column.
The posterior longitudinal ligament is significantly more narrow and therefore not quite as strong as its anterior counterpart.
It runs within the vertebral canal, along the posterior aspect of the vertebral bodies. The ligament extends from the C2 vertebra to the sacrum, and it attaches more to the intervertebral discs than to the posterior surfaces of the vertebral bodies.
This ligament helps to prevent hyperflexion, and it also prevents posterior herniation, or slipping, of the nucleus pulposus into the vertebral canal.Okay, now let’s take a deep breath and have a quick quiz!

Quiz3:39–3:56

Can you identify the parts of the intervertebral disc?Next, we are going to look at the joints of the vertebral arches, which are zygapophyseal joints, also known as the facet joints.

Joints of the vertebral arches3:56–4:45

The facet joints are synovial joints between the superior, And the inferior articular processes of adjacent vertebrae. They allow gliding movements of the adjacent articular processes.
The type and extent of movement that occurs at the facet joints is determined by the shape and arrangement of the articular processes, which varies within different regions of the vertebral column.
Each of the facet joints is surrounded by a thin joint capsule attached to the margins of the articular facets. The looser the joint capsule, the greater the mobility of the facet joint.
For example, cervical joint capsules are particularly loose, making them more mobile than other facet joints. Now, as important as mobility is for the vertebral column, it is also important that the structural integrity of the vertebral column is maintained and that nothing moves too far out of place.

Accessory ligaments4:45–6:22

This is where the accessory ligaments come in, namely the ligamenta flava, the interspinous and supraspinous ligaments, and the intertransverse ligaments.
The ligamenta flava, plural for ligamentum flavum, are broad ligaments that extend vertically to connect the laminae of adjacent vertebrae from C2 to S1, and they help form the posterior wall of the vertebral canal.
The ligamenta flava resist separation of the vertebral laminae during flexion and help maintain the normal curvature of the vertebral column.
Next up are the interspinous ligaments! These are weak, thin ligaments that connect the superior and inferior surfaces of adjacent spinous processes, which help limit flexion of the vertebral column.
On the other hand, the supraspinous ligaments form a strong, fibrous cord that connects the posterior tips of the spinous processes from C7 to the sacrum and also act to limit flexion of the vertebral column.
Above C7, the supraspinous ligament merges with the nuchal ligament, which is a strong, thick, and broad ligament. The ligament runs along the back of the neck & extends up to the posterior aspect of the skull, limiting flexion of the head.
Last but not least, the intertransverse ligaments extend vertically to connect the transverse processes of adjacent vertebrae, limiting lateral flexion of the spine.

Quiz6:22–6:32

Time for another break! Let’s pause and see if you can identify these ligaments?
Alright, now let’s get into the last group of joints of the vertebral column: the craniovertebral joints, which of course, join the cranium with the vertebral column.

Craniovertebral joints6:32–6:55

There are two sets of craniovertebral joints: the atlanto-occipital joints and the atlanto-axial joints, both of which are synovial joints that allow for a much wider range of motion than the rest of the joints of the vertebral column.

Atlanto-occipital joints6:55–8:28

So let’s break down the atlanto-occipital joints first! The term atlanto- comes from atlas, which is the C1 vertebra.
So, the atlanto-occipital joints are the articulation of the lateral masses of the atlas, which feature two concave superior articular surfaces, with the occipital condyles, which are the convex protuberances on each side of the foramen magnum.
These joints permit the flexion and extension movements when nodding “yes” or when head banging at a rock concert. To help us remember the movements that occur at these joints, we can think of them as the “YES” joints.
A small amount of lateral flexion and rotation is also permitted at these joints. Feel free to take a quick break and practice these moves to stretch your neck!
The cranium and the atlas are also connected by the anterior atlanto-occipital membrane and the posterior atlanto-occipital membrane.
The anterior atlanto-occipital membrane is broad and continuous with the anterior longitudinal ligament. It is made up of strong fibers that extend from the anterior arch of the atlas to the anterior margin of the foramen magnum.
The posterior atlanto-occipital membrane continues with the ligamentum flavum. It’s also broad, but made up of relatively thin and weak fibers that extend from the upper border of the posterior arch of the atlas to the posterior margin of the foramen magnum.
Together, the anterior and posterior atlanto-occipital membranes help prevent excessive movement of the atlanto-occipital joints.

Atlanto-axial joints8:28–10:52

Next, there are the atlanto-axial joints, which connect the C1 vertebra, or atlas, to the C2 vertebra, or axis. This is a complex joint that’s actually made up of a median, and two lateral synovial joints.
The lateral atlanto-axial joints connect the inferior facets of the lateral masses of the atlas to the superior facets of the axis.
The lateral atlanto-axial joints are plane type synovial joints, which only allow the atlas to glide over the axis. Next is the median joint.
This joint is between the anterior surface of the dens, or odontoid process, of the axis, and a facet that lies on the posterior surface of the anterior arch of atlas.
This unique articulation creates a pivot joint. The dens is held up against the anterior arch of the atlas by the transverse ligament of the atlas, which attaches to tubercles on the lateral masses of the atlas.
Movement at all three joints permits the cranium and atlas to rotate together as a unit on the axis, moving the head side to side, known as the ‘no’ movement.
To help us remember and distinguish these joints from the atlanto-occipital joints we can think of the atlanto-axial joints as the “NO” joints.
Now, looking from a posterior view of the skull, we can see that from the transverse ligament of the atlas, there are a pair of weak longitudinal bands that extend vertically.
The superior longitudinal band extends up to the occipital bone, and the inferior longitudinal band extends down to the body of the axis.
Together, the transverse ligament of the atlas and the superior and inferior longitudinal bands are known as the cruciate ligament of the atlas, named so because of its resemblance to a cross.There’s also a pair of short, fibrous cords called the alar ligaments which extend from both sides of the dens to the lateral margins of the foramen magnum to hold the dens in place, and prevent excessive rotation.Lastly, lying posterior to both the alar and cruciate ligaments is the tectorial membrane.
This ligament is the strong superior continuation of the posterior longitudinal ligament that extends from the body of the axis through the foramen magnum to the central part of the floor of the cranial cavity.
This membrane contributes to the stability of the upper cervical spine by limiting flexion and rotation.ATLAS-t! We are done with a bunch of CRUCIATE information about joints!

Quiz10:52–11:10

Now, JOINt me in taking a break to attempt to recall the important features of the craniovertebral joints. All right.
Now that we have talked about the different types of joints of the vertebral column, let’s take a closer look at the differences in movement at the cervical, Thoracic, and lumbar regions of the vertebral column.In the cervical region, flexion, extension, lateral flexion, and rotation are all possible.

Movements11:10–12:39

This is due to the atlanto-occipital and atlanto-axial joints, along with the horizontal orientation of the articular surfaces of the facet joints which allow for extensive gliding in all directions.
Finally, the neck is relatively thin, without a bulk of tissues surrounding the vertebral column, especially when compared to the trunk.In the thoracic region, movement is mainly in the form of rotation with some lateral flexion.
Flexion and extension are very limited because the facet joints are oriented in the coronal plane. Additionally, articulation with the ribs and the tissue bulk surrounding the thoracic vertebrae in the upper trunk combine to further limit the ability to flex or extend the thoracic vertebrae.Finally, the lumbar region is somewhat in between the cervical and thoracic region in terms of flexibility.
Similar to the cervical region, the joints of the lumbar region allow for plenty of flexion and extension as the facet joints are oriented in the sagittal plane.
However, the articulation of the facet joints in this area prevents rotation. Alright, time for another quiz before wrapping up!

Quiz12:39–12:50

Can you identify each of these movements of the vertebral column?Finally, the joints of the vertebral column also give it its overall shape.

Spine curvatures12:50–13:47

Looking at it from a lateral view, we can see how the spine curves differently in different regions. The thoracic and sacral regions curve to form anterior concavities, known as kyphoses, plural for kyphosis.
The thoracic and sacral curvatures are known as primary curvatures, meaning that they are retained from the original fetal curvature.
The cervical and lumbar regions curve to form posterior concavities, known as lordoses, plural for lordosis. The cervical and lumbar lordoses are secondary curvatures, meaning they develop after birth as a result of extension from the flexed fetal position.The cervical lordosis develops when an infant is able to hold up their head and the lumbar lordosis develops when the infant begins to walk.
These curvatures of the vertebral column collectively make the spine more flexible and more capable of bearing weight and absorbing shock.All right, as a quick recap.

Review13:47–15:17

The joints of the vertebral bodies are joined by strong intervertebral discs that help to cushion and absorb shock when weight-bearing.
The zygapophyseal, or facet joints, form between articular processes of adjacent vertebrae, and they allow for gliding movements.
Collectively, facet joints and their orientation allow for the different types of motion throughout the spinal column. The two craniovertebral joints are the atlanto-occipital which allows for flexion and extension, and the atlanto-axial joints which allows for rotation.
In the cervical region, flexion, extension, lateral flexion, lateral extension, and rotation are all possible. The thoracic region mainly permits rotation.
Some lateral flexion occurs, but flexion and extension are very limited. In the lumbar region, fairly extensive flexion and extension are possible, though minimal rotation can occur.Even though some regions have limited movement, the curvatures of the spine allow for ample movement of the vertebral column as a whole.
The normal curvatures of the spine include the kyphoses in the thoracic and sacral regions, which are primary curvatures, and the lordoses in the cervical and lumbar regions, which are secondary curvatures.