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Definition
INTRODUCTION
BIOMECHANICS OF Posture is the attitude assumed by •Static and Dynamic Posture
POSTURE the body either with support during
muscular inactivity,or by means of
•Posture Control
the co-ordinated action of many •Major Goals and Basic Elements
Dr Surendra Ojha muscles working to maintain stability of Control
Associate Professor
MPT Ortho/Musculosketetal
MGUMST JAIPUR

Static and Dynamic Erect bipedal stance

Quadrupedal stance
Posture
Advantage: freedom for upper
extremities -Body weight is distributed b/w
•Static- body and its segments are UE and LE
Disadv: -increases work of heart
aligned and maintained.Eg’s
-increase stress on -Large BOS and low COG
Sitting, Standing.
vertebral col.,pelvis,LE
•Dynamic- body or its segments are
moving.Eg’s Walking, Running -reduces stability
-small BOS and high COG

Postural Control
•Posture control depends on integrity
of CNS,visual, vestibular and
It is a persons’ ability-maintain musculoskeletal system
stability of body and body
•It also depends on information from
segments in response to forces receptors located in and around
that disturb the bodys’ joints (jt.capsules,tendons and
structural equilibrium ligaments) and from the sole of feet

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Major Goals and Basic -Absent or altered inputs:

Muscle synergies
Elements of Control •In absence of normal gravitational
- “PERTURBATION” is any sudden change in
force in weightless conditions during conditions that displaces the body posture away
Major goals: space flight from equilibrium
•Control the bodys’ orientation •Occurs in decreased sensation of LE Perturbation
-Altered outputs:
•Maintain bodys’ COG over BOS
•Inability of the muscles to respond sensory mechanical
•Stabilize the head vertically- eye app. to signals from the CNS (altering of visual (displacements- movts of
gaze is appropriately oriented input) body segments or of entire
• ms of a person in peripheral nerve
damage body)

Fixed-support synergies:
Postural responses to perturbations
caused by either platform or by pushes patterns of muscle activity in which
Synergies the BOS remains fixed during the
or pulls are called REACTIVE or
perturbation and recovery of
COMPENSATORY response
•Fixed- support synergies equilibrium
•stability is regained through
These responses are a.k.a SYNERGIES or •Change-in-support synergies movements of parts of the body
STRATEGIES but,the feet remain fixed on BOS
eg:Ankle synergy,Hip synergy

Ankle Synergy

Ankle synergy consists of discrete

bursts of muscle activity on either the
anterior or posterior aspects of the
body that occur in a distal-to-
proximal pattern in response to
forward and backward movements of
the supporting platform respectively

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Hip Synergy Change-in-support Synergies

Hip synergy consists of discrete •Includes stepping (forward,backward,

bursts of muscle activity sideways) and grasping (using one’s
opposite to ankle pattern in a hands to grasp a bar or other fixed
proximal-distal pattern of support) in response to movements of
activation the platform
•Maintains stability in the instance of
large perturbation

Head Stabilizing Strategies Strategies for maintaining the

vertical stability of head
•Proactive strategy: occur in •HSS : modification of head position
anticipation of initiation of in anticipation of displacements of
internally generated forces the body’s COG
•Head stabilization in space (HSS)

•Used in dynamic equilibrium •HST : head and trunk move as a

situation •Head stabilization on trunk (HST) single unit
Eg: maintain the head during
walking

Kinetics and Kinematics of Inertia Gravity

Posture
•In the erect standing posture the •Gravitational forces act
�External forces: Inertia,Gravity and body undergoes a constant swaying downward from the body’s COG
Ground Reaction Forces(GRF’s) motion called postural sway or sway
envelope
•Sway envelope for a normal •In static erect standing
�Internal forces: muscle posture,the LOG must fall
individual,standing with 4” b/w the
activity,passive tension in feet – 12° in sagittal plane and 16° within the BOS,which is
ligaments,tendons,jt. capsules and in frontal plane typically the space defined by
other soft tissue structures the two feet

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Ground Reaction Forces

•GRFV is equal in magnitude but
opposite in direction to the
gravitational force in erect standing
posture
•The point of application of GRFV is
at the body’s centre of pressure(COP)
•COP is located in the foot in
unilateral stance and b/w the feet in
bilateral standing postures

Optimal or Ideal Posture

Coincident Action Lines
-An ideal posture is one in which the -In normal standing posture,the
body segments are aligned vertically LOG falls close to,but not through
and LOG passes through all the jt. most jt. axes
The GRFV and the LOG have axes
coincident action lines in static erect -Normal body structures makes it -Compressive forces are distributed
posture impossible to achieve,but is possible to over the weight bearing surfaces of
attain a posture,close to ideal one jt’s; no excessive tension exerted on
ligamentous or required muscles

Analysis of Posture
•A plumb line is used to
represent the LOG
•Skilled observational analysis of
posture involves identification of the
location of body segments relative to •Postural analysis may be
the LOG performed using;
•Body segments-either side of LOG- radiography,photography,EMG,
symmetrical electrogoniometry,force plates,
3-dimensional computer analysis

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Lateral view- Deviations from optimal

alignment

•Vertebral coloumn:
•Foot and Toes:
-Claw toe
-Lordosis
-Hammer toe -Kyphosis
•Knee:
-Flexed Knee Posture •Head:
-Genu Recurvatum -Forward Head Posture
•Pelvis:
-Excessive Anterior Pelvic Tilt

Claw Toes

•Deformity of toes- hyperextension of MTP jt.,

flexion of PIP and DIP jt.’s
•Callus- dorsal aspect of flexed phalanges
•Affects all toes (2nd through 5th)

Hammer Toe
•Deformity-hyperextension of MTP and
DIP jt.’s
- flexion of PIP jt.
•Callus on superior surface of PIP jt.’s

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Lordosis

It refers to an abnormal
increase in the normal anterior
convexities of either the cervical
or lumbar regions of the
vertebral column

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Kyphosis

It refers to an abnormal increase in

the normal posterior convexity of
the thoracic vertebral column

Gibbus Dowager’s Hump

•a.k.a Hump Back is a deformity that •Found in post-menopausal women

may occur as result of TB with osteoporosis

•It forms a sharp posterior angulation •Anterior aspect of bodies of series of

in the upper thoracic region of vertebra collapse due to osteoporotic
vertebral column weakening and therefore, increase in
post. convexity of thoracic area

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Optimal alignment-Anterior aspect

Body
segments LOG location
• Head • Middle of forehead,nose,chin
• Chest • Middle of xyphoid process
• Abdomen/hips • Through umbilicus
• Hips/pelvis • Line equidistant from rt and lt
ASIS and through symphysis pubis
• Knees • Equidistant from medial femoral
condyles
• Ankles/feet • Equidistant from the medial
malleoli

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Optimal alignment-Posterior aspect Anterior-posterior View – Deviations from

the optimal alignment Pes Planus(flat foot)

•Foot and Toes: -Pes planus •It is characterized by reduced or absent

• Head • Middle of head
arch,which may be either rigid or flexible
• Shoulders/spine • Along vertebral column in a -Pes cavus
straight line,which should
-Hallux valgus
bisect the back into two •Talar head-displaced-ant.,med.,inf. and
symmetrical halves •Knees: -Genu valgum
• Hips/pelvis
causes depression of navicular bone and
• Through gluteal cleft of -Genu varum lenghthening of tibialis post. muscle
buttocks and equidistant from
-Squinting or cross-eyed patella
• Knees PSIS
• Ankles/feet -Grasshopper eyes patella •Navicular lies below the Feiss line and may
• Equidistant from medial jt. •Vertebral column: -Scoliosis even rest on the floor in severe conditions
aspects
• Equidistant from medial

Pes Cavus
•Rigid flat foot: it is a structural •The medial longitudinal arch of foot may
deformity where the medial be unusually high
longitudinal arch of foot is absent •A high arch is called pes cavus
in NWB,WB and toe standing
•It is a more stable position of foot than
•Flexible flat foot: the arch is pes planus,Wt. borne-lat. borders of foot
reduced during normal wt.
bearing,but reappears during toe •Lateral lig. and peroneus longus muscle
standing and non wt. bearing stretched

Hallux Valgus

•It is a very fairly common deformity- medial

deviation of the first metatarsal at
tarsometatarsal jt. and lateral deviation of
phalanges at MTP jt.

•Bursa on the medial aspect of first MTP head

may be inflammed- Bunion

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Genu Valgum (knock knee) Genu varum (bow legs)

•In genu valgum,mechanical axes of LE are •Knees are widely seperated when the feet
displaced lat. and patella may be displaced lat. are together
•Cortical thickening on medial concavity –
•If genu valgum exceeds 30° and persists on femur and tibia – increased compressive
beyond 8yrs of age – structural changes occur force
•Patella may be displaced medially
•Medial knee jt. structures – abnormal tensile
or distraction stress
•Lateral knee jt. Structures – abnormal
compressive stress

Squinting or Cross-Eyed Patella

•A.k.a in-facing patella Grasshopper Eyes Patella

•Tilted/rotated position of patella

•High laterally displaced position of patella
•Superior medial pole of patella faces
medially
•Patella faces upward and outward
•Inferior pole faces laterally

•Q-angle may be increased

Idiopathic Scoliosis
Scoliosis
•Lateral flexion moment present
•Deviation of vertebrae with rotation
Lateral deviations of a series of •Compression of vertebral body on the side of
vertebrae from the LOG in one or concavity of curve
more regions of the spine may •Therfore,inhibition of growth of vertebral body
indicate the presence of lateral spinal on that side
curvature •This leads to wedging of vertebra
•Shortening of trunk muscle on concavity
•Convexity- stretching of muscles,ligaments
and joint capsules

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Non-structural Scoliosis References

• Joint Structure and Function by Pamela K.
•A.k.a functional curves Levangie & Cynthia C. Norkin (5th Edition) .
•Can be reversed if the cause of
curve is corrected THANK YOU
•These curves are a result of
correctable imbalance such as limb
length discrepancy or a muscle
spasm

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