Biomechanics of the intervertebral joints
1. Regional vertebral anatomy
 spinal regions
 terminology for spinal curves
2. Individual vertebral anatomy
3. Intervertebral joints
 joint structure
 axes of motion and joint movements
 movements available in the various spinal regions
4. Sacroiliac (SI) joint
5. Ligamentous restraint on spinal motions
6. Forces
Axes of motion at intervertebral joints
JOINT
Atlanto-occipital (AO)
lateral view; univ. of houston
Atlanto-axial (AA)
AXIS
MOTION
lateral
flexion/extension
a-p
lateral flexion (limited)
vertical rotation
vertical rotation
Intervertebral joints below C2* ap
lateral
lateral flexion
flexion/extension
*Below C2, all the intervertebral joints are functionally triaxial:
vertical axis
located approximately through the posterior portion of the
annulus fibrosis
antero-posterior (AP)
axis
through center of vertebral disc
lateral axis
located approximately through the posterior portion of the
annulus fibrosis
Pelvic motion requires motion at the surrounding joints
When a person stands, with both lower limbs fixed on a surface, pelvic motion
requires hip motion. If the shoulders remain fixed as well, pelvic motion requires
lumbar motion. These relationships occur in three planes.
SAGITTAL
LUMBAR FLEXION
LUMBAR EXTENSION
DECREASED LUMBAR
LORDOSIS
INCREASED LUMBAR
LORDOSIS
POSTERIOR PELVIC TILT
ANTERIOR PELVIC TILT
HIP EXTENSION
HIP FLEXION
IF PELVIS IS LOW ON LEFT, HIGH ON RIGHT:
FRONTAL
RIGHT INTERVERTEBRAL LATERAL FLEXION
(SIDEBENDING)
RIGHT HIP JOINT ADDUCTION
LEFT HIP JOINT ABDUCTION
TRANSVERSE
LEFT FORWARD PELVIC ROTATION =LEFTWARD
LUMBAR ROTATION
COMPLEMENTARY HIP ROTATION
SACROILIAC (SI) JOINT


PLANAR JOINT WITH COMPLEX CONTOURED JOINT SURFACE.
MOTIONS INCLUDE:
 SACRAL TORSIONS
 INNOMINATE ROTATIONS
 ANTERIOR INNOMINATE ROTATION
 POSTERIOR INNOMINATE ROTATION
Ligaments restrain intervertebral motion
Smith, Weiss, and Lehmkuhl (1996, Fig.11-2, p.371) diagram these ligaments'
locations.
Anterior spinal ligaments (those located anterior to the spine's lateral or flexionextension axis) elongate with and, therefore, limit extension:

Anterior longitudinal ligament (1)
Posterior spinal ligaments (those located posterior to the spine's lateral or flexionextension axis) elongate with and, therefore, limit flexion:







Posterior longitudinal lig.
(2)
Ligamentum flavum (3)
Interspinous lig.(4)
Supraspinous lig.(5)
Ligamentum nuchae (an
elaboration of the
supraspinous ligament in
the cervical region)
Intertransverse lig.* (6)
Facet (zygapophysial) joint
capsules (7)
*Because of their lateral location, intertransverse ligaments (6) limit
sidebending to the opposite side, around the intervertebral joint's A-P axis.
Posterior ligamentous structures that are extrinsic to the spine also elongate with
and prevent flexion:

thoracolumbar fascia
FORCES PRODUCE MOVEMENT IN THE SPINE
Forces can be gravitational or muscular
1. in sagittal plane (around lateral axis)
 Anterior forces cause flexion
 Posterior forces cause extension
2. in frontal plane (around a-p axis)
 Forces to left of axis cause left sidebending.
 Forces to right of axis cause right sidebending.
3. in transverse plane (around vertical / longitudinal axis)

Any force that is not parallel to the spine will cause rotation.
References:
Smith, L.K., Weiss, E.L., & Lehmkuhl, L.D. (1996). Brunnstrom's clinical
kinesiology (5th ed.). Philadelphia: F.A. Davis.
Last updated 10-17-01 ©Dave Thompson PT
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