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* Please Note: The following article is provided by Body Mechanics for the sole purpose of
educating and informing our current and future patients.
An Integrated Model Of "Joint" Function And Its Clinical Application
by Diane Lee BSR FCAMT
Diane Lee BSR FCAMT ; This paper was presented at the 4th Interdisciplinary World Congress on Low Back Ache.
Revelations from recent research, together with the interdisciplinary sharing?of ideas facilitated by the past three World Congresses on Low Back and Pelvic?Pain, has lead to the development of a new model for understanding the lumbopelvic?region. This model is an integrated one in that it considers the impact of?structure (form or anatomy), function (forces and motor control) and the mind?(emotions & awareness) on human performance.
This model evolved from questions which addressed "Why are you in pain?" and "Why
are you unable to do the things you want to do?" as opposed to "What
structure is causing you pain?" To answer the "WHY" questions
we need to understand how forces are controlled and transferred through the
body. This functional requirement has been called "effective load sharing",
effective force closure" or "effective load transfer" (Lee & Vleeming
2000). In short, how well can the individual stabilize their bones and joints
during both static and dynamic activities. Optimal stabilization requires accommodation
to each specific load demand, through adequate, tailored joint compression,
by muscles, fascia and ligaments. (Vleeming, Lee, Ostgaard, Sturesson, Mens).
Stability (both to sustained and intermittent loading) can only occur when
the passive, active and control systems work together to transfer load safely
and efficiently (Panjabi 1992). Adequate approximation of the joint surfaces
must be the result of all forces acting across the joint if stability is to
be insured. Adequate means not too much, not too little, but just enough. Consequently,
the ability to effectively transfer load through joints is dynamic and requires:
intact bones, joints and ligaments (form closure (Snijders et al 1993a,b)- first?component).
optimal function of the muscles which includes the ability of muscles?to contract tonically in a sustained manner (force closure (Snijders et?al 1993a,b) - second component) as well as the ability of the muscles to?perform in a co-ordinated manner (motor control - third component)?such that the resultant force is adequate compression through the articular?structures at an optimal point (tailored).
appropriate neural control, which ultimately orchestrates the pattern?of motor control. This requires constant accurate afferent input from the?mechanoreceptors in the joint and surrounding soft tissues, appropriate?interpretation of the afferent input and a suitable motor response (emotions?and awareness - fourth?component).
For every individual, there are many strategies available to achieve stability.
These are based on the individual's anatomical/biomechanical factors
(i.e. connective tissue extensibility, muscle strength, body weight, joint
surface shape, motor control patterns), psychosocial factors and the loads
they need to control.
We have learned that stability is not about amplitude of motion but rather
about how well an individual can control the amount of movement they have.
When motion control is inadequate, there may be too much or too little compression
of the joint surfaces. In both cases, the resultant afferent input is distorted
and sustains the ineffective motor control. Too much compression over a long
period of time will wear out the joints and lead to osteoarthritis. Too little
compression creates episodes of giving way and collapse.
This Integrated Model of "Joint" Function can be applied to every
region of the body - the following is an application to the pelvis.
First Component - Form ClosureThe sacroiliac joint transfers large loads and its shape is adapted to this
task. The articular surfaces are relatively flat and this helps to transfer
compression forces and bending moments (Snijders et al 1993ab). However, a
relatively flat joint is vulnerable to shear forces. The sacroiliac joint is
protected from these forces in three ways. Firstly, the sacrum is wedge-shape
in both the anteroposterior and vertical planes and thus is stabilized by the
innominates. Secondly, in contrast to other synovial joints, the articular
cartilage is not smooth but rather irregular, even at birth (Sashin 1930, Bowen & Cassidy
1981). Thirdly, a frontal dissection through the sacroiliac joint reveals cartilage
covered bone extensions protruding into the joint (Vleeming et al 1990a,b),
the so called ridges and grooves. They seem irregular, but are in fact complementary
and this serves to stabilize the joint when compression is applied. This stable
situation with closely fitting joint surfaces where no extra forces are needed
to maintain the state of the system, given the actual load situation, is called "form
closure" (Vleeming et al 1990, Snijders et al 1993 ab).
For many decades, it was thought that the sacroiliac joint was immobile due
to the close fitting nature of the articular surfaces. Research in the last
two decades has shown that mobility of the sacroiliac joint is not only possible
(Egund et al 1978, Lavignolle et al 1983, Sturesson et al 1989, 1999), but
essential for shock absorption during weight bearing activities. It has also
been shown (Vleeming et al 1992b) that the sacroiliac joint retains its mobility
with age. The quantity of motion available at this joint has been investigated
(Jacob & Kissling 1995, Sturesson 1989, 1997, 1998) with highly sophisticated
imaging and motion analysis techniques and the results reflect the wide anatomical
variance. It is known that the angular motion available at the sacroiliac joint
is very small (no more that 10 - 40 Sturesson 1989, 1997, 1998) and that this
motion couples with a very small amount of linear translation (less than 2
mm Sturesson 1989). The direction of motion coupling has been hypothesized
by Lee (1999) and recently confirmed by Hungerford et al (2001).
This research addresses the question "How much does the sacroiliac joint
move?" The answer - it moves a little bit and the amount varies
between individuals. No manual diagnostic tests have shown reliability for
determining how much an individual's sacroiliac joint is moving in either
symptomatic or asymptomatic subjects. What has been shown (Buyruk et al 1997)
through Color Doppler Imaging studies is the wide variation in stiffness values
of the sacroiliac joint in both symptomatic and asymptomatic subjects. Within
the same subject, the asymptomatic individual had similar values of stiffness
for both sacroiliac joints, whereas the symptomatic individual had different
values for the left and right sacroiliac joint. In keeping with this research,
perhaps the focus of manual motion testing should be how resistant the joint
is to an applied force rather than how much the sacroiliac joint is moving
and how symmetric the left and right SIJ's are.
To analyze stiffness we need to consider the zones of motion available to every
joint, the neutral zone and the elastic zone. The neutral zone (Panjabi 1992)
is a small range of movement near the joint's neutral position where
minimal resistance is given by the osteoligamentous structures. The elastic
zone is the part of the motion from the end of the neutral zone up to the physiological
limit. Panjabi noted (1992) that joints have nonlinear load-displacement curves.
The non-linearity results in a high degree of laxity in the neutral zone and
a stiffening effect toward the end of the range of motion. He has found that
the size of the neutral zone may increase with injury, articular degeneration
and/or weakness of the stabilizing musculature and that this is a more sensitive
indicator than angular range of motion analysis for detecting instability.
We hypothesized (Lee & Vleeming 1998, 2000) that the neutral zone may
also be effected by altering compression across the joint. To explain this
further we need to understand the second component of this model - force
closure.
Second Component - Force ClosureIf the articular surfaces of the sacrum and the innominate fit together with
perfect form closure, mobility would be practically impossible. However, form
closure of the sacroiliac joint is not perfect and mobility is possible, albeit
small, and therefore stabilization during loading is required. This is achieved
by increasing compression across the joint at the moment of loading. The anatomical
structures responsible for this are the ligaments, muscles and fascia. When
the sacroiliac joint is compressed, friction of the joint increases (Vleeming
et al 1990 a, b) and consequently augments form closure. The mechanism of compression
of the sacroiliac joints due to extra forces is called "force closure" (Vleeming
et al 1990, Snijders et al 1993ab). Force closure reduces the size of the neutral
zone and thus shear is controlled between the two joint surfaces.
Several ligaments, muscles and fascial systems contribute to force closure
of the pelvis. When working efficiently, the shear forces between the innominate
and sacrum are adequately controlled and loads can be transferred between the
trunk, pelvis and legs.
In what position is the pelvic girdle the most stable? Studies have shown
(Egund 1978, Lavignolle 1983) that sacral nutation (forward motion of the sacral
promontory) occurs bilaterally when moving from sitting to standing and that
full nutation occurs during forward (Sturesson 1998) or backward bending of
the trunk. This motion tightens the major ligaments of the posterior pelvis
(sacrotuberous, sacrospinous, interosseus) (Vleeming et al 1989a,b, Wingerden
et al 1993) and this tension increases the compressive force across the sacroiliac
joint. Ligaments can increase articular compression when they are tensed or
lengthened by the movement of the bones to which they attach. Alternately,
they can increase articular compression when they are tensed by contraction
of muscles that insert into them. Tension in the sacrotuberous ligament can
be increased by posterior rotation of the innominate relative to the sacrum,
nutation of the sacrum relative to the innominate or by the contraction of
the muscles that attach to it (biceps femoris, piriformis, gluteus maximus,
multifidus). The main ligamentous restraint to counternutation of the sacrum,
or anterior rotation of the innominate, is the long dorsal sacroiliac ligament
(Vleeming et al 1996, Vleeming 1998). This is a relatively less stable position
for the pelvis to resist horizontal and/or vertical loading since the sacroiliac
joint is under less compression and is not self-locked.
By themselves, ligaments cannot maintain a stable pelvis. They rely on several
muscle systems to assist. There are two important groups of muscles that contribute
to stability of the low back and pelvis. Collectively they have been called
the inner unit (core) and the outer unit (sling systems). The inner unit consists
of the muscles of the pelvic floor, transversus abdominis, multifidus, the
diaphragm and the posterior fibers of psoas - the core, also known as
the local stabilizers (Gibbons & Comerford 2001). The outer unit consists
of several slings or systems of muscles (global stabilizers and mobilizers
(Gibbons & Comerford 2001)) that are anatomically connected and functionally
related.
The Inner Unit - The CoreHodges & Richardson (Hodges & Richardson 1996, 1997a, Richardson & Jull
1995, Richardson et al 1999) have shown that transversus abdominis is a primary
muscle for stabilization of the low back and pelvis. It has a large attachment
to the middle layer and the deep lamina of the posterior layer of the thoracodorsal
fascia(TDF) and is recruited prior to the initiation of any movement of the
upper or lower extremity (Hodges & Richardson 1996). Its contraction is
hypothesized to increase compression across the anterior aspect of the pelvis
and thus increase force closure of both the sacroiliac joint in its anterior
aspect and the pubic symphysis in its superior aspect. Its contraction also
increases the tension in the thoracodorsal fascia (Hodges & Richardson
1996, Vleeming et al 1997). The secondary effect of this increase in TDF tension
is thought to be compression of the sacroiliac joints.
Multifidus is contained between the lamina of the lumbar vertebra and sacrum
and the deep layers of the thoracodorsal fascia. When it contracts, it broadens
and therefore increases the tension of the TDF. Hides et al (1994) found segmental
wasting and local inhibition of the lumbar multifidus muscle in all patients
with a first episode of acute/subacute low back pain. In a followup study (Hides
et al 1996), they found that without therapeutic intervention, multifidus did
not regain its original size or function and the recurrence rate of low back
pain over an eight month period was very high. The "pump-up action" and
stiffening of the TDF is therefore lost in these patients. Compression of the
posterior pelvis would therefore be reduced. Clinically, it appears that co-activation
of transversus abdominis and multifidus increases the stiffness value of the
sacroiliac joint facilitating the force closure mechanism of the pelvis.
The function of the four parts of the levator ani muscle and the inter-relationship
between the pelvic floor and the abdominals has revealed (Sapsford et al 1998)
a co-activation pattern between pubococcygeus and transversus abdominis. The
pubococcygeus and transversus abdominis help to force close (stiffen) the pubic
symphysis (pubococcygeus inferiorly and TA superiorly) and prevent excessive
shearing of the symphysis during activation of the adductors (hypothesis).
It is thought that the pelvic floor and sacral multifidus act as a force couple
to control the position of the sacrum. When the sacrum is slightly nutated
by the proper activation of these two muscles, the pelvis and the lumbosacral
junction are more stable.
Bridging the diaphragm and the pelvic floor, it has been suggested (Gibbons & Comerford
2001) that the posterior fibers of psoas act as a local stabilizer of segmental
motion in concert with the deep fibers of multifidus. Further research into
the timing of activation of psoas under low and high loads is required - the
hypothesis is that the posterior fibers are re-anticipatory. Anatomically,
it is interesting to note that the fascia which envelopes psoas is directly
connected to the fascial origin of both the pelvic floor and the diaphragm
(Gibbons & Comerford 2001).
The Outer Unit - The Integrated Sling SystemIn the past, four systems have been described that comprise the outer unit
of muscles - the posterior oblique, the anterior oblique, the longitudinal
and the lateral (Table 1). Although these muscles can be trained individually
(topographically), effective force closure requires specific co-activation
and release for optimal function.
Recognizing that individual muscles are important for stabilization
as well as for mobility, it is critical to understand how they connect and work
together in functional systems. When muscles contract, they produce a force that
spreads beyond the origin and insertion of the active muscle. This force is transmitted
to the muscles, tendons, fascia, ligaments, capsules and bones that lie both
in series and in parallel to the active muscle. In this manner, forces are
produced quite distant from the origin of the initial muscle contraction. These
integrated muscle systems produce slings of forces that assist in the transfer
of load through 'tension sharing' or tensegrity.
Tensegrity is a term popularized by Buckminster Fuller when he built the first geodesic dome.
These buildings transfer loads through tension beams which are connected in
triangles. The integrity of this tension system is crucial to the stability
of the structure (tension integrity = tensegrity). When a force pulling in
one direction is equally opposed by a force pulling in the opposite direction,
stability is achieved for that direction of force only. For complete rigidity
of a structure the various lines of force form a series of isosceles triangles.
These are called tensegrity structures. Our bodies do not require this amount
of rigidity, in fact our function would be limited because of it. However,
the linking together of muscles through their connective tissue bonds (fascia,
ligaments and bones) can create momentary tensegrity systems that assist in
the transference of force without too much compression through the joints.
Exercises, which connect muscles both individually and collectively, provide
tensegrity for the direction of load being imposed.
The integrated sling system represents forces and is comprised of several muscles. A muscle may participate
in more than one sling and the slings may overlap and interconnect depending
on the task being demanded. There are several slings of myofascial systems
in the outer unit. These include, but are probably not limited to, a coronal
sling (has medial and lateral components) a sagittal sling (has anterior and
posterior components) and an oblique spiral sling. The hypothesis is that the
slings have no beginning or end but rather connect as necessary to assist in
the transference of forces. It is possible that the slings are all part of
one interconnected myofascial system and the sling (coronal, sagittal or oblique)
which is identified during any particular motion is merely due to the activation
of selective parts of the whole sling.
The identification and treatment of a
specific muscle dysfunction (weakness, inappropriate recruitment, tightness)
is important when restoring force closure (second component) and for understanding
why parts of a sling may be restricted in motion or lacking in support. Exercises,
which restore specific muscle length and strength, are second component exercises
in this model. Exercises that integrate the muscles together in tensegrity
sling systems retrain the third component - motor control.
Third Component - Motor
Control Motor control pertains to the patterning of muscle activation, in other words
the timing of specific muscle action and release and is not a birthright. Superb
motor skills require co-ordination of muscle action such that stability is
ensured and loads are transferred effortlessly.
Integrated exercises, which
focus on sequenced muscle activation, are necessary for restoring motor control.
Some of these methods include Pilates, Feldenkrais, Somatics and some forms
of Yoga and Tai Chi. Janda, Sahrmann, Hodges, Richardson, O'Sullivan
and Comerford approaches to muscle balance and exercise also fit into this
model at the 3rd component.
Fourth Component - Emotions & Awareness Recently, more focus is being given to the effect of emotions on motor control
and muscle activation. As a clinician, it is imperative to understand the powerful
effect thoughts and motivation can have on outcome and to seek professional
assistance when necessary. In addition, it is understood that awareness of
both the emotional state and awareness when exercising can have a dramatic
impact on functional outcomes.
When an exercise is taught emphasizing learning
(focused and attentive), motor control patterns can be changed. Conversely,
when the exercise environment is noisy, attention is lacking and exercises
are often done without considering how the motion is occurring (ie. 10 repetitions
at 10 kilos no matter what) and faulty patterns are often reinforced. This
is when exercise can actually be harmful and the patient's symptoms made
worse. The reader is referred to the article by Vleeming in this proceedings
for further information on the role of emotions and awareness on motor control.
Clinical
Application of the Integrated Model of "Joint" Function Impaired
pelvic function can be defined as an inability to effectively transfer forces
through the pelvis. To reach this diagnosis, specific clinical tests that analyse
form closure, force closure, motor control and emotional states are required.
Since pain on movement is not a criteria from which a biomechanical diagnosis
can be made (Bogduk 1997), pain provocation tests do not assist in reaching
this diagnosis. Pain provocation tests look for nociceptive generating structures
and belong to the "WHAT" question and not the "WHY".
To reach a biomechanical diagnosis (WHY) we need to evaluate pelvic function
with simple tests that have the potential to meet scientific scrutiny for reliability
and validity.
The following clinical tests were initially described in the proceedings
of the 3rd World Interdisciplinary Congress on Low Back and Pelvic Pain and
only the relevant updated information will be presented in this article.
Quebec
Back Pain Disability Scale This functional questionnaire has been used
at the Spine and Joint Centre in Rotterdam for several years now and research
has been conducted (Mens et al submitted) on its efficacy to evaluate the course
of recovery in peripartum pelvic pain patients. Each participant in the program
completed this questionnaire at their initial visit and then again after 8
weeks of treatment. The test scores have been co-related with hip abduction/adduction
strength as well as the findings of the Active Straight Leg Raise Test (ASLR)
(see Mens 2001). The QBPDS rating scale is from 0 - 100. Mens found that
sensitivity for pelvic impairment was greatest when the results from this test
were greater than 45. All patients who scored greater than 45 on this test
had a positive Active Straight Leg Raise meaning they had difficulty (increased
effort or pain) while performing the ASLR. The scale is a useful way to measure
the impact of disability and the impact of treatment programs.
Gait Greenman (1997) has described the biomechanics of the
pelvis necessary to achieve a smooth efficient gait. When pelvic impairment
is present, marked deviations in the coronal plane (waddling gait) occur (Lee
1997). Part of Mens' (2001)
doctoral study investigated the validity and reliability of reduced hip abduction
and adduction strength as a diagnostic instrument in posterior pelvic pain
as a consequence of pregnancy. He found a significant reduction in the strength
of both hip abduction and adduction in the pelvic pain group compared to controls
and suggests that "Weakness of the abduction strength explains why patients
with severe PPPP (peripartum pelvic pain) have a waddling gait. When abduction
strength decreases and body weight increases it is no longer possible to keep
the pelvis horizontal during one-leg stance. To avoid this problem, the patient
places the center of gravity of the trunk above the hip of the weight-bearing
leg."
Sagittal Plane Motion - Forward and Backward Bending This
test examines the ability of the low back and pelvis to control both vertical
and horizontal shear forces during segmental sagittal rotation while forward
or backward bending the trunk. When the leg lengths are equal, the pelvic girdle
flexes symmetrically at the hip joints and the sacrum remains nutated bilaterally
throughout the forward bending motion (Sturesson 1989, 1999). No intrapelvic
torsion should occur, in other words the PSIS's
should remain level. In backward bending, the pelvic girdle extends symmetrically
at the hip joints and the sacrum remains nutated bilaterally. Asymmetry of
motion of the innominates during forward or backward bending is NOT indicative
of any specific dysfunction since many articular and myofascial problems can
produce this finding. When unstable, loads are not easily transferred through
the low back or pelvis when the trunk moves in the sagittal plane.
One Leg Standing With Contralateral Hip Flexion The clinical relevance of any motion analysis between the innominate and the
sacrum on the non-weight bearing side during this test has been challenged
by Sturesson (1998). In his RSA studies of women with suspected hypermobility
of the sacroiliac joint, he found that minimal (0.20 ) motion actually occurred
on the non-weight bearing side. He concluded that this movement too small to
be reliably palpated and that this test should not be used to determine mobility
of the sacroiliac joint.
It remains useful for testing the ability of the patient
to transfer load through one lower extremity while flexing the contralateral
hip. During this maneuver the sacrum should nutate on the weight bearing side
(Sturesson 1998, Hungerford et al 2001a, b) facilitating the transference of
load to one leg. This should occur smoothly with minimal adjustments of the
lower extremity and the pelvis should remain in its original coronal plane.
Active
Straight Leg Raise This test was developed by Mens & Vleeming (1997,
1999, 2001) to evaluate load transfer through the pelvic girdle in the non-weight
bearing position. While supine, the patient is asked to lift one leg with the
knee extended. Their ability to do so without bulging their abdomen, rotating
or sidebending their trunk and pelvic girdle is observed and their effort to
perform the task is noted. Force closure of the pelvic girdle is then augmented
by applying a gentle compression force through the pelvis. The active straight
leg raise test is repeated and any change in the motor pattern (ability to
stabilize the pelvis in a neutral position) and in their effort is noted.
Variations
of the test have been developed (Lee 2001) to facilitate exercise prescription
for core stabilization. The action of the inner unit core muscles (local stabilizers)
can be simulated by varying the location of the compression force prior to
the ASLR. Approximation of the ASIS's (anterior compression)
simulates the action of transversus abdominis, approximation of the PSIS's
(posterior compression) simulates the action of multifidus and approximation
of the pelvis at the level of the pubic symphysis simulates the action of the
pelvic floor. Improvement in the ASLR during specific pelvic compression assists
in the development of individual exercise programs (Lee 2001).
Neutral
Zone Analysis With And Without Activation Of The Force Closure Mechanism These
tests examine the ability of the sacroiliac joint to resist vertical and horizontal
translation forces (shear) that are applied passively to the non-weight bearing
joint and have been described in detail elsewhere (Lee 1997, 1998, 1999). When
analysing the results from these tests it is important to remember that stability
is NOT about how much movement there is or isn't
but rather about the stiffness value the system has. Buyruk et al (1997) found
that unstable sacroiliac joints had lower stiffness values and that symptomatic
individuals demonstrated asymmetry in the values between their left and right
sides. The force displacement curve (stiffness value) or rather the response
of the innominate to the pressure (sense of resistance or sense of easily giving
way) is noted and then compared to the patient's opposite side. We cannot
make any judgements regarding amplitude of motion (stiff, loose, normal) with
this test since it has been shown that the range of motion at this joint is
highly variable and making a statement regarding the amplitude implies knowledge
of what is "normal". It is not possible to know what the patient's
normal should be. We can only compare the left to the right side of the pelvis
and look for symmetry of stiffness values. Echodoppler studies of the effect
of both the local stabilizers (inner unit muscles) and the global mobilizers
(outer unit sling systems) on stiffness of the SIJ (force closure) will be
presented at this congress (see proceeding articles by Richardson & Hides,
Wingerden & Vleeming). Resting muscle tone as well as subtle activation
of muscles can effect force closure of the pelvis and thus stiffness of the
SIJ. This must be taken into consideration when interpreting the results of
these tests. This fact is also significant when inter-tester reliability studies
are considered for motion analysis of the SIJ, either passive, as in joint
play testing, or active.
These studies support the clinical hypothesis (Lee
1999) that when force closure is effective, it will reduce the size of the
neutral zone, increase the friction of the joint surfaces and thus increase
the resistance to shear forces at the SIJ. Alternately, sustained, overactivation
of these same muscles (too much compression) can restrict any motion of the
SIJ. Optimal function requires adequate, and appropriately timed, compression
and release of the sacroiliac joint.
To test the efficacy of force closure of
the pelvic girdle, the patient is first instructed to recruit their inner unit
(Richardson et al 1999) while maintaining a normal breathing pattern. This
instruction may take a few sessions to master. Once the patient is able to
sustain an isolated contraction of the inner unit, the effect of this contraction
on the neutral zone is assessed by repeating the anteroposterior and vertical
shear tests after the patient has force closed the pelvis. The stiffness value
should increase and no relative motion between the innominate and sacrum should
be felt.
A biomechanical diagnosis can now be made regarding the stability
of the pelvic girdle and the ability of the system to transfer and sustain
a load.
Impaired Pelvic Function Optimal stabilization of the pelvis
requires accommodation to each specific load demand, through adequate, tailored
joint compression, by muscles and ligaments. (Vleeming, Lee, Ostgaard, Sturesson,
Mens). Biomechanically, there are only two things that can go wrong with the
sacroiliac joint - it's ability
to move can become restricted or its mobility can be poorly controlled. In
this model, we (Lee & Vleeming 1998, 2000) prefer to call this too much
or too little compression which results in inappropriate force closure and
subsequently ineffective load transfer.
Panjabi's concept of the ball
in the bowl (1992) and the broadening of this concept has been previously described
(Lee & Vleeming 1998, 2000).
What follows is the clinical application of this concept into the "Integrated
Model of "Joint" Function". Hopefully, the following will
clarify how essential all of the different clinical approaches (manual therapy,
exercise, education) are in the management of patients with pelvic impairment.
It is illogical to attempt to "prove" that one approach is better
than another since each will have relevant clinical application for specific
impairments.
Excessive articular compressionExcessive compression across the sacroiliac joint can result from true articular
pathology such as ankylosing spondylitis or fibrosis of the capsule secondary
to trauma. While a fused SIJ cannot be mobilized with manual therapy techniques,
a fibrosed joint is easily mobilized in one or two treatment sessions when
specific, localized, passive techniques are used (Lee 1998, 1999). This is
an impairment of the first component of this Integrated Model of "Joint" Function - form
closure. Manual therapy is an essential part of the treatment of this impairment.
Excessive
compression of the joints of the pelvis can also be caused by inappropriate
muscle forces. When an individual develops a stabilization strategy that uses
predominantly the posterior pelvic floor and the deep external rotators of
the hip joint, the constant activation of these muscles overly compresses the
inferior aspect of the sacroiliac joint (Lee 2001).
This is an impairment of
the second component of this Integrated Model of "Joint" Function - force
closure. While manual therapy (passive SIJ mobilization or manipulation, muscle
energy technique, pressure-stretch techniques, strain/counterstrain) may assist
in relieving the inferior pelvic compression, unless the motor control strategy
for stabilization is addressed, the dysfunctional pattern is likely to recur.
The specific muscles that are weak must be strengthened, those which are tight
must be lengthened. Addressing individual muscle function is treatment of the
second component of this model - force closure. However, once the individual
is able to isolate and activate the local stabilizers they must learn to sequence
the timing of this muscle activation prior to any loading through the trunk,
arms and/or legs. This is treatment of the third component of this model - motor
control. Exercises need to be prescribed according to individual impairments
and the reader is referred to the references for further information on this
(Richardson et al 1999, Lee 1999, 2001). The Active Straight Leg Raise Test
can help direct the selection of exercises by noting which part of the system
requires more compression and which requires less. Recently, we have been using
imagery (Lee 2001, Franklin 1996) to facilitate the learning process - a
longstanding technique of dancers and athletes.
Impairments of this componentExcessive articular compression with an underlying instability When
a force is applied to the sacroiliac joint sufficient to attenuate the articular
ligaments (fall on the buttocks or a lift/twist injury), the muscles will
respond to prevent dislocation and further trauma to the joint. The resulting
spasm fixes the joint in an abnormal resting position and marked asymmetry
of the pelvic girdle (innominate and/or sacrum) is present. This is an unstable
joint under excessive compression and commonly occurs unilaterally. This is
an impairment of both form and force closure in that the relationship between
the articular surfaces has been disturbed and the muscle response is excessive.
Treatment of this individual which focuses on exercise without first addressing
the "posture", "position", alignment" of the
pelvis tends to be ineffective and commonly increases symptoms. Conversely,
if treatment only includes manual therapy (mobilization, manipulation or muscle
energy) for correction of "posture", "position", "alignment",
relief tends to be temporary and dependence on the health care practitioner
providing the manual correction is common.
Treatment requires a specific distraction
manipulation (form closure - first
component) (Lee 1998, 1999, Hartman 1997) to reduce the articular compression
and restore the symmetric resting position of the pelvis. Repeat analysis of
the neutral zone will now reveal a decrease in the stiffness of the effected
SIJ compared to the opposite side. Treatment now requires the restoration of
force closure (second component) and motor control (third component) with an
individually prescribed exercise program. In the meantime, the temporary application
of a sacroiliac belt is often useful to augment the force closure mechanism.
This
impairment requires manual therapy first followed by exercise and education
for a successful outcome.
Insufficient articular compression This situation arises when
there is either inadequate or inappropriate motor control such that there is
insufficient articular compression during movement and loading. The cause can
be a single major trauma, a repetitive minor trauma (habitual postures), hormonal
or systemic. The patient often complains of sensations of giving way or a lack
of trust when loading through the involved extremity. This impairment is readily
apparent during the one leg standing test and the ASLR test. During one leg
standing, the weight bearing innominate anteriorly rotates (Hungerford 2001)
when the contralateral hip is flexed. During the ASLR test, the pelvis commonly
rotates to the side of the elevating leg. Associated with this, is over-activation
of the posterior pelvic floor and under-activation of the transversus abdominis
and anterior pelvic floor. Other common substitution strategies for stabilization
will be found in Hodges and Richardson's
work and the video Imagery for Core Stabilization (Lee 2001).
Once again, this
is an impairment of the second and third component of the Integrated Model
of "Joint" Function and the focus of treatment
is exercise and education.
Conclusion The Integrated Model of "Joint" Function was developed in an attempt
to understand the past and present research pertaining to the pelvis and patients
with pelvic pain. With this model, we can now establish sound inclusion criteria
for further studies of treatment outcomes. Patients can be investigated according
to their impairment as opposed to the location of their pain. This integrated
model requires integrated treatment protocols that are reasoned clinically
and can be researched for efficacy in a more logical manner. With this model,
we can begin to answer the "WHY" questions and provide the evidence-based
treatment demanded by health care payer.
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