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Chapter 27
The Sacroiliac Joint
Overview

The sacroiliac joint (SIJ), which serves
as the point of intersection between
the spinal and the lower extremity
joints is the least understood and,
therefore, one of the most
controversial and interesting areas of
the spine
Anatomy
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The ilium, ischium, and pubic bone
fuse at the acetabulum to form each
innominate
Each of the two innominates articulate
with the sacrum, forming the sacroiliac
joint, and with each other at the
symphysis pubis
Anatomy


The sacrum is a strong and triangular
bone located between the two
innominates
Provides stability to this area and
transmits the weight of the body from
the mobile vertebral column to the
pelvic region
Anatomy

The articulating surfaces of the sacroiliac
joint differ
– The iliac joint surfaces are formed from
fibrocartilage
– The sacral surfaces are formed from hyaline
cartilage.
– The hyaline cartilage is 3-5 times thicker than
the fibrocartilage, so that between the sacral
and iliac auricular surfaces, the sacroiliac joint is
deemed a synovial articulation, or diarthrosis
Anatomy

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The configuration of the sacroiliac
joints is extremely variable from
person to person, and between
genders in terms of morphology and
mobility
These differences are not pathological,
but are normal adaptations
Anatomy

Like other synovial joints, the
sacroiliac joint is reinforced by
ligaments, but the ligaments of the
sacroiliac joint are some of the
strongest and toughest ligaments of
the body
Anatomy
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The anterior sacral ligament (ASL) is an
anterior-inferior thickening of the fibrous
capsule
Relatively weak and thin compared to the
rest of the sacroiliac ligaments
Extends between the anterior and inferior
borders of the iliac auricular surface, and
the anterior border of the sacral auricular
surface
Anatomy
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
The interosseous ligament is a short
ligament located deep to the dorsal
sacroiliac ligament
Forms the major connection between
the sacrum and the innominate, filling
the irregular space posterior-superior
to the joint between the lateral sacral
crest, and the iliac tuberosity
Anatomy

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
The dorsal sacroiliac ligament (long
ligament) connects the PSIS (and a small
part of the iliac crest) with the lateral crest
of the third and fourth segment of the
sacrum
This is a very tough and strong ligament
Sacral nutation (anterior motion) of the
sacrum appears to slacken this ligament
whereas counternutation (posterior motion)
tautens the ligament
Anatomy



The sacrotuberous ligament is comprised of
three large fibrous bands, broadly attached
by its base to the posterior inferior iliac
spine, the lateral sacrum, and partly
blended with the dorsal sacroiliac ligament
Stabilizes against nutation (forward rotation)
of the sacrum
Counteracts against the dorsal and cranial
migration of the sacral apex during weight
bearing
Anatomy


The sacrotuberous ligament extends
from the ischial spine to the lateral
margins of the sacrum and coccyx,
and laterally to the spine of the
ischium
Counteracts against nutation of the
sacrum
Anatomy


The pubic symphysis is classified as a
symphysis as it has no synovial tissue
or fluid, and contains a
fibrocartilaginous disc
The bone surfaces of this joint are
covered with hyaline cartilage, but are
kept apart by the presence of the disc
Anatomy

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Thirty-five muscles attach directly to
the sacrum and/or innominate
These muscles primarily function to
stabilize the sacroiliac joint rather than
to move it
Anatomy
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The piriformis muscle
Primarily functions to produces external
rotation and abduction of the femur
Also thought to function as an internal
rotator and abductor of the hip if the hip
joint is flexed beyond 90°
Capable of restricting sacroiliac joint motion
Anatomy

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The term “pelvic floor muscles” primarily refers to
the levator ani, a muscle group composed of the
pubococcygeus, puborectalis and iliococcygeus
The levator ani muscles join the coccygeus muscles
to complete the pelvic floor
The pelvic floor muscles work in a coordinated
manner to increase intra-abdominal pressure,
provide rectal support during defecation, inhibit
bladder activity, help to support the pelvic organs,
and assist in lumbopelvic stability
Anatomy

Neurology
– It remains unclear precisely how the anterior
and posterior aspects of the sacroiliac joint are
innervated, although the anterior portion of the
joint likely receives innervation from the
posterior rami of the L2-S2 roots
– Contribution from these root levels is highly
variable and may differ among the joints of
given individuals
– It is the joint’s highly variable and complex
innervation that produces a very diffuse pattern
of pain referral from this area
Biomechanics
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The pelvic area must function to absorb the
majority of the lower extremity rotation,
while still permitting motion to occur
It is likely, that the movement of the pelvis
is in the nature of deformations and slight
gliding motions around a number of
undefined axes, with the joints of the pelvic
ring deforming in response to body weight
and ground reaction forces
Biomechanics

There is very little agreement, either
among disciplines, or even within
disciplines about the biomechanics of
the pelvic complex. The results from
the numerous studies on mobility of
the sacroiliac joint have led to a
variety of different hypotheses and
models of pelvic mechanics over the
years
Biomechanics

Osteopathic model
– The sacrum rotates around two oblique
axes
– The innominates are capable of rotating
anteriorly and posteriorly
– Distinction made between sacroiliac
impairment and iliosacral impairment
Biomechanics

Chiropractic model
– As one innominate flexes, the ipsilateral
sacral base moves anterior and inferior,
and as the other innominate extends, the
sacral base on that side moves posterior
and superior
Biomechanics

Biomechanical model
– When the sacrum nutates, or flexes,
relative to the innominate, a linear glide
occurs between the two L-shaped
articular surfaces of the sacroiliac joint.
The shorter of the two lengths, level with S 1,
lies in a vertical plane
 The longer length, spanning S 2-4, lies in an
anterior-posterior plane

Biomechanics
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
Snijders and Vleeming defined kinetics
within the lumbar/pelvic/hip region by
introducing the concepts of ‘extrinsic’ and
‘intrinsic’ stability of the pelvic girdle and the
‘self-locking’ mechanism
Their work instituted the terms form closure
and force closure to describe the passive
and active forces that help to stabilize the
pelvis and the sacroiliac joint
Biomechanics

Form closure
– Form closure refers to a state of stability within
the pelvic mechanism, with the degree of
stability dependent upon its anatomy, with no
need for extra forces to maintain the stable state
of the system
– Relies on incongruity of the articular surfaces,
the friction coefficient of the articular cartilage
and the shape of the articulating surfaces
Biomechanics

Force closure
– Force closure requires intrinsic and extrinsic
forces to keep the sacroiliac joint stable
– These dynamic forces involve the neurological
and myofascial systems, and gravity. Together,
these components produce a self-locking
mechanism for the sacroiliac joint
– Critical to the self-locking mechanism is the
ability of the sacrum to nutate
Examination

Under the premise that a relationship
between pelvic asymmetry and low back
pain exists, orthopedic, osteopathic, and
physical therapy texts promote the use of
pain provocation (symptom-based) tests
and biomechanical (mechanical-based) tests
that include static (positional) and dynamic
(motion or functional) tests
Examination
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Given the questionable reliability and validity
of the tests for the sacroiliac joint, the
clinician should guard against forming a
diagnosis based on the results of a few tests
Ideally, the diagnosis needs to be based on
the results from a thorough biomechanical
examination that includes pain provocation
and static and dynamic tests
Examination

As several recent studies have found
improved inter-rater reliability in the
diagnosis of low back pain when using
a combination of physical examination
procedures as opposed to a single
model approach, it might be logical to
assume that a similar approach would
work with the SIJ
Examination

History that indicates SIJ dysfunction
– A history of sharp pain awakening the patient
from sleep upon turning in bed
– Pain with walking, ascending or descending
stairs, standing from a sitting position, or with
hopping or standing on the involved leg
– A positive straight leg raise at, or near, the end
of range (occasionally early in the range when
hyperacute), pain, and sometimes limitation, on
extension and ipsilateral side bending of the
trunk
Examination
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Systems Review
– Given the number of visceral organs in
the vicinity of the sacroiliac joint, a
thorough systems review is needed to
rule out a visceral source for the
symptoms
Examination
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Observation
– An examination of posture is performed
to check for the presence of asymmetry
– However, as pelvic landmark asymmetry
is probably the norm, ‘positive findings’
are to be expected
Examination
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Hip Range of Motion
– The evidence to demonstrate whether hip
rotation is limited in patients with signs of
sacroiliac joint dysfunction is inconclusive
Examination
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Palpation of bony landmarks
– An altered positional relationship within
the pelvic girdle should only be
considered positive if a mobility restriction
of the sacroiliac joint and/or pubic
symphysis is also found
Examination

Weight bearing and non-weight bearing
kinetic tests
– These tests are designed to assess the
osteokinematics occurring at the sacroiliac joint
during patient generated movements
– The tests assess the mobility of the innominate,
and the ability of the sacrum to nutate
(ipsilateral test), and to side bend (contralateral
test)
Examination

The short and long-arm tests
– These tests are used to confirm or refute
the findings from the kinetic tests
Examination

Sacroiliac Joint Stress Tests
– Designed to assess the integrity of the
joint and the surrounding ligaments
– Believed to be sensitive for severe
arthritis or ventral ligament tears,
although they have been shown to be
poorly reproducible
Intervention

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Thus far, the success of interventions
at this joint has been mixed, due in
part to the poor reliability with many
of the examinations used
The success of any intervention
depends on the quality and accuracy
of the examination and the
subsequent evaluation
Intervention
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
It follows that if the examination gives an
inaccurate diagnosis, the intervention may
have a mixed result
Given that the chosen intervention for the
sacroiliac joint, like the spine, depends
largely on the philosophy or background the
clinician uses to establish the diagnosis, a
variety of diagnoses for the same
biomechanical dysfunction can arise
Intervention

Acute phase goals:
– Decrease pain, inflammation, and muscle spasm
– Increase weight bearing tolerance, where appropriate
– Promote healing of tissues through sufficient stabilization
(may require belt)
– Increase pain-free range of sacroiliac joint motion
– Regain soft tissue extensibility around the pelvic region
– Regain neuromuscular control
– Allow progression to the functional stage
Intervention

Functional phase goals:
– To significantly reduce or to completely resolve
the patient’s pain
– To restore full and pain-free sacroiliac joint range
of motion
– To integrate the lower kinetic chains into the
rehabilitation
– Complete restoration of gait, where appropriate
– The restoration of pelvic and lower quadrant
strength and neuromuscular control