SPINAL BIOMECHANICS
POSTURE ANALYSIS
POSTURE
• Keep in mind the spine is found at the posterior
aspect of the body, behind the center of gravity
• Center of gravity lies:
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Through the atlanto-occipital joint
Tragus of the ear
Anterior humeral head
Anterior-inferior edge of T11
Greater trochanter
Just behind the patella
Through the lateral malleoli
DURING POSTURAL ANALYSIS…
• Usually stance is asymmetrical if not intentional.
• The weight of the body is borne by the skeleton aided by the
action of intrinsic back muscles
• Sway occurs during stance.
• Postural sway of the vertebral column on the pelvis is
controlled by the erector spinae, and the rectus abdominis.
• 80% of the contraction occurs in the E.S., whereas only 20% of
contraction occurs in the abdominals, as confirmed by EMG
studies.
• In scoliosis, E.S. contraction is higher on the convex side.
AFFECTS OF AXIAL
COMPRESSIVE FORCES
• Increases from the C/S to the L/S
• Lumbar problems are common--#1 reason to see a
Chiropractor
HOW DO MUSCLES
BECOME IMBALANCED?
• Skeletal misalignment- triggers other muscles to be
recruited to restore normal posture
• Joint pain or malformation- imbalance in stance and
gait
• Ligamentous injury/instability- recruits muscles to
support the joint
• Muscle fatigue- recruits other muscles to contract to
accomplish the same movement, often resulting in
myofascial trigger points
BEGINNING POSTURE ANALYSIS
• Work from the “ground-up”:
– Check for any lower extremity deformity that may be
creating imbalance above
EXAMINE THE FEET
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LONGITUDINAL ARCH
PRONATION
SUPINATION
MEDIAL MALLEOLI LEVELS
ACHILLES TENDON POSITION
SIGNS OF LIGAMENTOUS LAXITY
Pes Planus
Pes Cavus
REASONS BEHIND
TOE-IN & TOE-OUT
• TOE-IN
– INTERNAL TIBIAL ROTATION
Blount's disease
– TIBIA VARUS
– INCREASED INTERNAL ROTATION of FEMUR —often due to
muscular contraction/imbalance
• TOE-OUT
– BILATERAL- SACRAL ANTERIORITY
– UNILATERAL- PELVIC ANTERIORITY
– INCREASED EXTERNAL ROTATION of FEMUR—often due to
muscular contraction/imbalance
EXAMINE THE KNEES
• FLEXED
– Hamstring spasm
– Quad weakness
– Acute low back pain
• HYPEREXTENDED
– Ligamentous
– Anterior compression
fracture
KNEES
GENU VARUS
GENU VALGUS
Q – ANGLE
(Quadriceps)
• Wide Hips (female runners)
• Knock Knees (·Genu
valgum)
• Pronation of the feet
• Subluxating Patella
• High riding patella (patella
alta)
• Weak Vastus Medialis
An abnormally high Q-Angle can cause stress on the
entire kinetic chain of the lower extremity causing
many conditions from low back pain to foot pain.
D. Robert Kuhn, DC, Terry R. Yochum, DC, Anton R.
Cherry, Sean S.Rodgers
Imbalance of Hip Rotators
• Leg length discrepancies and
foot pronation may lead to:
• Iliotibial band syndrome
• Piriformis syndrome
• Recurrent muscle strains (hamstring and
groin pulls) can be an indicator of asymmetry
in structural alignment.
HIP MUSCLES…
• Transfer ground-reaction forces from legs to
trunk during gait
• Supply coordinated propulsion
• Provide balanced stability for the pelvis and
spine
• Through repetitive use patterns and after
injuries, hip muscles may become shortened
and/or weak
[1] Kim D. Christensen, DC, CCSP, DACRB
THIGH AND PELVIS
• BULK OF HAMSTRINGS
• GREATER TROCHANTERS
• PELVIC TILT, SWAY (antalgia),
TORTION- AS or PI
• ILIAC CREST LEVELS
• PSIS LEVELS
• SACRAL ROTATION (S2—PSIS distance)
• GLUTEAL MUSCLES- Deeper Dimpling
POSTURAL ANALYSIS
P-A View
• Sacral Base– Level
– Held in place by innominate bones
– Dependant upon equal leg lengths
• What can go wrong?
– Sacral deformity» Transitional segment
» Plateau base
– Anatomical short leg
» Congenital
» Acquired
– Functional
» Due to muscle imbalance
» Due to pelvic distortion
BODY RESPONDS IN A PREDICTABLE
MANNER
• Attempts to restore balance:
– Eyes on horizontal plane “Righting Reflex”
– Equally distributing weight to center of gravity
VERTICAL PLANE of LUMBAR SPINE
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SPINOUS ALIGNMENT
SECTIONAL TOWERING
CURVATURE
LORDOSIS
PARASPINAL MUSCLE TONICITY
SKIN DISCOLORATION
THORACIC OBSERVATIONS
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SPINOUS ALIGNMENT
SECTIONAL TOWERING
CONVEXITY or SCOLIOSIS
+ ADAM’S SIGN
KYPHOSIS
RIB HUMP
SCAPULAR WINGING (myopathies, shoulder
instability, Serratus anterior weakness)
• POSTERIOR SCAPULA (scoliosis)
• HIGH SHOULDER/TRAP
• INTERNAL ROTATION HUMEROUS
NECK and HEAD OBSERVATIONS
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C2 SPINOUS ALIGNS WITH S2 TUBERCLE?
MASTOID PROCESS LEVELS
HEAD TILT OR ROTATION
ANTERIOR HEAD CARRIAGE
LORDOSIS
MUSCLE TONE
LATERAL VIEW
• SACRUM: Inclines from 26-56º from horizontal
– LUMBAR: Levels off at L4 superior body surface
(Apex), continues posteriorly in upper L/S
– THORACIC: Gradual reversal of curve: body wedging
to create kyphosis at apex (T4-T6)
– CERVICAL: Curve reverses again: apex (C4)
• What constitutes postural abnormality?
– Any Variation in the AP or Lat
» Pelvic unleveling
» Spinal segment unleveling
• Produces imbalance & altered weight imposition
Kendall, et. al.
FROM THE SIDE
KYPHOSIS
LORDOSIS
NORMAL RANGES of MOTION
• Varies
– Age
– Activity
• EVALUATE: As a total unit; comparing symmetry
more than degrees
– Break it down by section—if blocked in one section
may lead to hypermobility in another
– Look for:
• Abnormal coupling of motion (rotation with flexion)
• Bilateral symmetry; smoothness & ease of motion
MOTION
T/L
C
FLEXION
90
60
EXTENSION
40
50
UNILAT ROTATION
30
80
UNILAT LAT
35
45
FLEXION
SACROILIAC KINETICS
THE SACROILIAC JOINT
A Controversial Topic
Complicated Anatomy
and Biomechanics:
1. Small ROM
2. Passive movement
3. Stress-relieving joint
MOTION IN THE S/I JOINT
• No gross excursion (except due to severe trauma)

Movement: Normal physiological effect of shock
absorption
– Obvious movement during ambulation-Sacral nutation
• Clear osseous limitation– Interlocking ridges & grooves
– Strong reinforcing ligaments
– Key-stone in arch stability
• Age Factors in degree of motion:
– Flexible—to—Ankylosis
Gillett’s test …
Demonstrates pelvic motion by comparing PSIS
motion B/L:
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Fixation
Pseudo-ankylosis
Fusion
Lumbar or hip muscle hypertonicity
Pelvis Tips and Rotates
in Accommodation…
A response to dysfunction
above or below
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Leads to:
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Abnormal: unequal weight into each S/I joint
leading to…
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Pelvic distortion
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Eccentric weight imposition into each S/I joint
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Abnormal posture
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Abnormal gait
PELVIC DISTORTION IS PREDICTABLE…
• Predictable patterns of accommodation have been
demonstrated as a response to imbalance both above
and below.
• Therefore, pelvic distortion is often not a primary
subluxation, but a compensatory, secondary distortion
PRIMARY SUBLUXATION IN THE
LUMBAR SPINE
(Secondary S/I Dysfunction)
 IVD HERNIATION
 CURVATURE OR SCOLIOSIS
 TRANSITIONAL SEGMENT
ALTERED SAGITTAL CURVE
FUNCTIONAL: GROSS MUSCULAR
PRIMARY DISTORTION DUE TO LOWER
LIMB DEFICIENCY
(Secondary S/I Dysfunction)
• ANATOMICALLY SHORT FEMUR OR TIBIA
• GENU VARUM OR VALGUS
• PRONATION
• FLAT FOOT
• HIP, KNEE, ANKLE OR FOOT PAIN
PRIMARY
Sacroiliac Fixation
•
Chronic stress to the S/I joints leads to:
– Repetitive microtraumas
– Gross muscular compensation—holding joint
in the fixed malposition
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May eventually lead to :
– Sclerotic changes
PRIMARY
Sacroiliac Instability
• Sprain
• Pregnancy & Child Birth
• Pubic Symphysis Dysfunction
CHARACTERISTICS OF S/I PAIN
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Painful to walk
Ascending or descending stairs
Standing from a sitting position
Hopping or standing on involved leg
Sharp pain that awakens the patient
from sleep upon turning in bed
What Research Has Shown
• L/S may refer pain to S/I
• S/I ROM:
– Decreases with age
– Minimal compared to spine
• Pain can=
– 1° Fixation, Instability or
– 2° Accommodation
CONTINUED S/I JOINT STRESS…
• May lead to true fixation in its misalignment—
becoming a primary subluxation
– Prolonged accommodation to chronic spinal
subluxation and postural abnormality or leg deficiency
may lead to
• Fixation
• Gross muscular change
• Sclerosis
OTHER ENTITIES CAUSING S/I JOINT
PAIN
• Pelvic disorders- Prostatitis, Interstitial Cystitis, or
breast, lung or prostate metastasis
• Enteric disorders- Iliopsoas abscess (Diabetes, UTI)
• Inflammatory arthrotides or
“Spondyloarthropathies”- A.S, Lupus, Reactive
Arthritis (“Reiter’s”), Crohn’s disease
EXAMINATION
1.
2.
3.
4.
5.
6.
Observation
Primary Stress Tests
Leg Length Tests
Weight Bearing Kinetic Tests
Secondary Stress Tests
Orthopedic Tests
I. OBSERVATION
Pages 88-90
1. Postural Analysis:
1. Pelvic tilt (Anterior or Posterior)
2. Lateral pelvic tilt
3. Any structural asymmetry
2. Check for landmark:
1. Alignment
2. Tenderness
3. Belt Test: Test to R/O lumbar involvement
REINERT SPECIFIC LISTINGS FOR
PELVIC DISTORTIONS AS RELATED TO THE
SACROILIAC JOINT
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POSTERIOR
POSTERO-INFERIOR
INFERIOR
ANTERIOR
ANTERO-SUPERIOR
SUPERIOR
II.
PRIMARY STRESS TESTS
LEG LENGTH
WEIGHT-BEARING
KINETIC TESTS
Sacral Compression Test
Forced
Counternutation
GAENSLEN’S
TEST
YEOMAN’S TEST
FABER PATRICK’S TEST
HIBB’S TEST
PRONE PALPATION
MOTION PALPATIONComparing Symmetry
1. PRONE PASSIVE: Spring S/I joints
2. SEATED PASSIVE: Spring S/I joints
3. PRONE ACTIVE: Stabilize S/I joints and ask
patient to extend lower limb while knee
remains extended
CONCLUSION
• Determine if S/I pain is 1° or 2 °
• Once this is achieved, the doctor can
determine the appropriate treatment