Dr. Ali Selk Ghafari: Biomechanics of Musculoskeletal System: Components of the Musculoskeletal System

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Lecture 1: Components of the
Musculoskeletal System
By: Dr. Ali Selk Ghafari
Email: a_selkghafari@sharif.edu
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1.1 Chapter Outline
In this lecture you will learn about:
• Components of the musculoskeletal system
• Section I – Skeletal tissue and skeletal system
• Section II – Muscular tissues
• Section III – Joints
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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1.2 Components of the Musculoskeletal System
• Components of the Musculoskeletal System
• Skeletal tissues
• Muscular tissues
• Joints
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Section I: Skeletal Tissues and Skeletal System
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I.1 Terminology
• osteology – the study of bone
• skeletal system – composed of bones, cartilages, & ligaments
• cartilage – forerunner of most bones, covers many joint
surfaces of mature bone
• ligaments – hold bones together at the joints
• tendons – attach muscle to bone
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I.2 Cartilage
Cartilage
• Supplementary to bone providing
strength, rigidity and some elasticity.
• Hyaline cartilage forms the
temporary skeleton of bone and the
articular surfaces of synovial joints.
• White fibrocartilage has great tensile
strength and is able to resist
compressive stresses.
• Yellow fibrocartilage contains elastic
fibres.
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I.3 Functions of the Skeleton
• support – hold the body up, supports muscles, mandible and
maxilla support teeth
• protection – brain, spinal cord, heart, lungs
• movement – limb movements, breathing, action of muscle on
bone
• electrolyte balance – calcium and phosphate ions
• acid-base balance – buffers blood against excessive pH
changes
• blood formation – red bone marrow is the chief producer of
blood cells
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I.4 Shapes of Bones
Sutures
Sutural
bone
Vertebra
Carpal
bones
Parietal bone External table
Internal
table
Diploë
(spongy
bone)
Humerus
Patella
Sutural Bones Flat Bones
Long Bones
Sesamoid Bones
Irregular Bones
Short Bones
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I.5 General Features of Bones
• compact (dense) bone – outer shell of long bone
• diaphysis (shaft) - cylinder of compact bone to provide leverage
• medullary cavity (marrow cavity) - space in the diaphysis of a long bone
that contains bone marrow
• epiphyses - enlarged ends of a long bone
• enlarged to strengthen joint and attach ligaments and tendons
• spongy (cancellous) bone covered by more durable compact bone
• skeleton about three-fourths compact and one-fourth spongy bone by weight
• spongy bone found in ends of long bones, and the middle of nearly all others
• articular cartilage – a layer of hyaline cartilage that covers the joint
surface where one bone meets another
• allows joint to move more freely and relatively friction free
• nutrient foramina – minute holes in the bone surface that allows blood
vessels to penetrate
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 periosteum – external sheath that covers bone except where there is
articular cartilage
– outer fibrous layer of collagen
• some outer fibers continuous with the tendons that attach muscle to bone
• perforating (Sharpey’s) fibers – other outer fibers that penetrate into the bone
matrix
• strong attachment and continuity from muscle to tendon to bone
– inner osteogenic layer of bone forming cells
• important to growth of bone and healing of fractures
 endosteum – thin layer of reticular connective tissue lining marrow cavity
– has cells that dissolve osseous tissue and others that deposit it
 epiphyseal plate (growth plate) – area of hyaline cartilage that
separates the marrow spaces of the epiphysis and diaphysis
– enables growth in length
– epiphyseal line – in adults, a bony scar that marks where growth plate used to be
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Living (b) Dried
Marrow cavity
Periosteum
Nutrient foramen
Site of endosteum
Compact bone
Spongy bone
Epiphysis
Epiphysis
Diaphysis
Articular
cartilage
Epiphyseal
line
Red bone
marrow
Yellow bone marrow
Epiphyseal
line
Articular
cartilage
Suture
Outer compact
bone
Spongy bone
(diploe)
Inner compact
bone
Trabeculae
structure of a long bone structure of a flat bone
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I.6 Bone Development
• ossification or osteogenesis – the formation of bone
• in the human fetus and infant, bone develops by two
methods:
• intramembranous ossification
• endochondral ossification
• Intramembranous ossification – produce the flat bones of the skull and
most of the clavicle (collar bone).
• Endochondral ossification – process in which bone develops from pre-
existing cartilage model. Most bones develop by this process.
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I6.1 Intramembranous Ossification
Mesenchymal cell
Blood capillary
Osteoid tissue
Osteocyte
Calcified bone
Osteoblasts
Fibrous periosteum
Osteocytes
Trabeculae
Osteoblasts
Osteoblasts
Spongy bone
Compact bone
Marrow cavity
Fibrous periosteum
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Sheet of condensing
mesenchyme
Condensation of mesenchyme into soft sheet
permeated with blood capillaries
Honeycomb of bony trabeculae formed by
continued mineral deposition; creation of
spongy bone
Trabecula
Deposition of osteoid tissue by osteoblasts
on mesenchymal surface; entrapment of first
osteocytes; formation of periosteum
Surface bone filled in by bone deposition,
converting spongy bone to compact bone.
Persistence of spongy bone in the middle layer.
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I.6.2 Endochondral Ossification
Perichondrium
Bony collar
Periosteum
Metaphysis
Diaphysis
Epiphysis
Cartilage
Metaphysis
Spongy bone
Marrow cavity
Compact bone
Periosteum
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Early cartilage model1
3 4 5 6
Hyaline
cartilage
Enlarging
chondrocytes
Primary
ossification
center
Secondary
ossification
center
Blood
vessel
Primary
marrow
cavity
Secondary
marrow cavity
Secondary
ossification
center
Epiphyseal
plate
Nutrient
foramen
Articular
cartilage
Epiphyseal
line
Adult bone with a
single marrow
cavity and closed
epiphyseal plate
Bone of child, with
epiphyseal plate at
distal end
Bone at birth, with
enlarged primary
marrow cavity and
appearance of
secondary marrow
cavity in one epiphysis
Vascular invasion,
formation of primary
marrow cavity, and
appearance of
secondary
ossification center
Formation of
primary
ossification center,
bony collar, and
periosteum
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I.7 Composition of Bone
Composition of Bone Bone Contains …
99% of the body’s Calcium
4% of the body’s Potassium
35% of the body’s Sodium
50% of the body’s Magnesium
80% of the body’s Carbonate
99% of the body’s Phosphate
Calcium 39%
Potassium 0.2%
Sodium 0.7%
Magnesium 0.5%
Carbonate 9.8%
Phosphate 17%
Total inorganic
components
67%
Organic
compounds
(mostly collagen)
33%
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SEM  25Normal spongy bone
Spongy bone in osteoporosis SEM  21
I.8 Osteoporosis
Spinal Osteoporosis
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I.9 Overview of the Skeleton
• two regions of the skeleton
– axial skeleton – forms the central supporting axis of the body
• skull, auditory ossicles, hyoid bone, vertebral column, and thoracic cage
(ribs and sternum)
– appendicular skeleton – includes the bones of the upper limb and
pectoral girdle, and the bones of the lower limb and pelvic girdle
• number of bones
– 206 in typical adult skeleton
• varies with development of sesamoid bones (patella)
– bones that form within some tendons in response to stress
• varies with presence of sutural (wormian) bones in skull
– extra bones that develop in skull suture lines
– 270 bones at birth, decreases with fusion
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I.10 Axial Skeleton
• Structures of the Axial
Skeleton
• Articulations
• Contacts with other bones
• Landmarks (marks)
• Areas of muscle and
ligament attachment
• Foramina
• Openings for nerves and
blood vessels
• Functions of the Axial
Skeleton
• Supports and protects
organs in body cavities
• Attaches to muscles of
head, neck, and trunk
• Performs respiratory
movements
• Stabilizes parts of
appendicular skeleton
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I.10 Axial Skeleton
• The Axial Skeleton
• Has 80 bones
1.The skull
• 8 cranial bones
• 14 facial bones
2.Bones associated with
the skull
• 6 auditory ossicles
• The hyoid bone
3. The thoracic cage
• 24 ribs
• The sternum
4. The vertebral column
• 24 vertebrae
• The sacrum
• The coccyx
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SKELETAL SYSTEM 206
APPENDICULAR SKELETON
Cranium
Hyoid
Sternum
Ribs
Vertebrae
Sacrum
Coccyx
Associated
bones
Skull
Face
Skull and
associated
bones
Thoracic
cage
Vertebral
column
AXIAL SKELETON
Auditory
ossicles
`8
14
6
1
1
24
24
1
1
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I.10 Axial Skeleton
An anterior view of the entire skeleton, with the axial components highlighted.
The numbers in the boxes indicate the number of bones in the adult skeleton.
© 2012 Pearson Education, Inc.
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I.11 The Vertebral Column
• Functions of the Vertebral Column (Spine)
• Protects the spinal cord
• Supports the head and body
• 26 bones
• 24 vertebrae, the sacrum, and the coccyx
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Spinal Curves
Primary curves develop
before birth, and secondary
curves after birth.
The cervical curve, a
secondary curve, develops as
the infant learns to balance the
weight of the head on the
vertebrae of the neck.
The thoracic curve, a
primary curve,
accommodates the
thoracic organs.
The lumbar curve, a
secondary curve, balances
the weight of the trunk over
the lower limbs; it develops
with the ability to stand.
The sacral curve, a
primary curve,
accommodates the
abdominopelvic organs.
Vertebral Regions
Regions are defined
by anatomical
characteristics of
individual vertebrae.
Cervical
(7 vertebrae)
Thoracic
(12 vertebrae)
Lumbar
(5 vertebrae)
Sacral
Coccygeal
I.11 The Vertebral Column
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I.12 The Thoracic Cage
• Functions of the Thoracic Cage
1. Protects organs of the thoracic cavity
• Heart, lungs, and thymus
2. Attaches muscles
• For respiration
• Of the vertebral column
• Of the pectoral girdle and the upper limbs
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• Ribs (Costae)
• Are 12 pairs of long, curved, flat bones
• Extending from the thoracic vertebrae
• Ribs are divided into two types
1. True ribs
2. False ribs
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• Ribs 1–7 (True Ribs)
• Vertebrosternal ribs
• Connected to the sternum by costal cartilages
• Ribs 8–12 (False Ribs)
• Do not attach directly to the sternum
• Vertebrochondral ribs (ribs 8–10)
• Fuse together
• Merge with cartilage before reaching the sternum
• Floating or vertebral ribs (ribs 11–12)
• Connect only to the vertebrae and back muscles
• Have no connection with the sternum
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Jugular notch
Clavicular articulation
Manubrium
Sternum Body
Xiphoid
process
Costal
cartilages
An anterior view, showing the
costal cartilages and the sternum
True ribs
(ribs 1–7)
False ribs
(ribs 8–12)
Floating ribs
(ribs 11–12)
Vertebrochondral
ribs
(ribs 8–10)
1
2
3
4
5
6
7
8
9
10
11
12
T12
T11
T1
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False ribs
(ribs 8–12)
A posterior view, showing the
articulations of the ribs and vertebrae
True ribs
(ribs 1–7)
1
2
3
4
5
6
7
8
9
10
11
12
1
2
3
4
5
6
7
8
9
10
11
12
C7
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
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I.13 The Appendicular Skeleton
• The Appendicular Skeleton
• 126 bones
• Allows us to move and manipulate objects
• Includes all bones besides axial skeleton
• The limbs
• The supportive girdles
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Clavicle
Pectoral
girdle
Upper
limbs
Scapula
Humerus
Radius
Ulna
Carpal
bones
Metacarpal
bones
Phalanges
Pelvic
girdle
Hip bone
SKELETAL SYSTEM
AXIAL SKELETON APPENDICULAR SKELETON
206
80 126
4
2
60
16
10
28
2
2
2
2
22
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Lower
limbs
Femur
Patella
Tibia
Fibula
Tarsal bones
Metatarsal
bones
Phalanges
2
2
2
2
60
14
10
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Page  31 Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Section II: Muscular Tissues
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II.1 Organization of Muscles
• about 600 human skeletal muscles
• constitute about half of our body weight
• three kinds of muscle tissue
– skeletal, cardiac, smooth
• specialized for one major purpose
– converting the chemical energy in ATP into the mechanical energy of
motion
• myology – the study of the muscular system
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II.2 The Functions of Muscles
• Movement
– move from place to place, movement of body parts and body contents in
breathing, circulation, feeding and digestion, defecation, urination, and
childbirth
– role in communication – speech, writing, and nonverbal communications
• Stability
– maintain posture by preventing unwanted movements
– antigravity muscles – resist the pull of gravity and prevent us from falling or
slumping over
– stabilize joints
• Control of openings and passageways
– sphincters – internal muscular rings that control the movement of food, bile,
blood, and other materials
• Heat production by skeletal muscles
– as much as 85% of our body heat
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II.3 Connective Tissues of a Muscle
• endomysium
– thin sleeve of loose connective tissue surrounding each muscle fiber
– allows room for capillaries and nerve fibers to reach each muscle fiber
• perimysium
– slightly thicker layer of connective tissue
– fascicles – bundles of muscle fibers wrapped in perimysium
– carry larger nerves and blood vessels, and stretch receptors
• epimysium
– fibrous sheath surrounding the entire muscle
– outer surface grades into the fascia
– inner surface sends projections between fascicles to form perimysium
• fascia
– sheet of connective tissue that separates neighboring muscles or muscle
groups from each other and the subcutaneous tissue
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Skeletal Muscle
Muscle Fascicle
Muscle Fiber
Epimysium
Surrounded by:
Epimysium
Contains:
Muscle fascicles
Perimysium
Surrounded by:
Perimysium
Contains:
Muscle fibers
Endomysium Surrounded by:
Endomysium
Contains:
Myofibrils
II.3 Connective Tissues of a Muscle
Skeletal muscle
Perimysium
Endomysium
Muscle fascicle
Perimysium
Epimysium
Nerve
Blood vessels
Muscle fiber
Tendon
Fascia
Muscle fiber
Muscle fascicle
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II.4 Classification of Muscles
• fusiform muscles
– thick in middle and tapered at ends
• parallel muscles
– have uniform width and parallel fascicles
– can span longer distances than other shapes
• triangular (convergent) muscles
– fan-shaped, broad at origin and tapering to a narrower insertion
• pennate muscles
– fascicles insert obliquely on a tendon (feather shaped)
– unipennate, bipennate or multipennate
• circular muscles (sphincters)
– ring around body opening
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• fusiform muscles can shorten quickly over a large distance
but have limited power.
• pennate muscles are more powerful but cannot shorten to
the same extent.
• isotonic muscle contraction involves a change in muscle
length often under constant force generation: in concentric
contraction the muscle shortens, while in eccentric
contraction it lengthens.
• isometric contraction involves no change in muscle length
but is usually associated with a change in the tension
generated.
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Fusiform
Parallel
Triangular
Unipennate
Bipennate
Multipennate
Circular
Biceps brachii
Rectus abdominis
Pectoralis major
Palmar interosseous
Rectus femoris
Deltoid
Orbicularis oculi
Tendon
Tendon
Belly
strength of a muscle and the direction of its pull are
determined partly by the orientation of its fascicles.
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II.5 Muscle Attachments
• indirect attachment to bone
– tendons bridge the gap between muscle ends and bony
attachment
• very strong structural continuity from muscle to bone
• direct (fleshy) attachment to bone
– little separation between muscle and bone
– muscle seems to immerge directly from bone
• some skeletal muscles do not insert on bone, but in dermis
of the skin – muscles of facial expression
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II.5 Muscle Attachments
• Origin
– bony attachment at stationary
end of muscle
• Belly
– thicker, middle region of
muscle between origin and
insertion
• Insertion
– bony attachment to mobile
end of muscle
Scapula
Bellies
Radius
Insertion
Humerus
UlnaInsertion
Origins Origins
Long head
Extensors:
Lateral head
Flexors:
Biceps brachii
Brachialis
Triceps brachii
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II.6 Functional Groups of Muscles
• action – the effects produced by a muscle
– to produce or prevent movement
• prime mover (agonist) - muscle that produces most of force
during a joint action
• synergist - muscle that aids the prime mover
– stabilizes the nearby joint
– modifies the direction of movement
• antagonist - opposes the prime mover
– relaxes to give prime mover control over an action
– preventing excessive movement and injury
– antagonistic pairs – muscles that act on opposite sides of a joint
• fixator - muscle that prevents movement of bone
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Section III: Joints
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III.1 Terminology
• joint (articulation) – any point where two bones meet,
whether or not the bones are movable at that interface
• arthrology – science of joint structure, function, and
dysfunction
• kinesiology – the study of musculoskeletal movement
– a branch of biomechanics – deals with a broad variety of
movements and mechanical processes in the body,
including the physics of blood circulation, respiration, and
hearing
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III.2 Joint Classification
• joint name – typically derived from the names of the bones
involved
– atlanto-occipital joint, glenohumeral joint, radioulnar joint
• joints classified according to the manner in which the
adjacent bones are bound to each other, with differences in
how freely the bones can move
• four major joint categories:
– bony joints
– fibrous joints
– cartilaginous joints
– synovial joints
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III.2.1 Bony Joint (Synostosis)
• bony joint, or synostosis – an immovable joint formed
when the gap between two bones ossify, and they become
in effect, a single bone
– frontal and mandibular bones in infants
– cranial sutures in elderly
– attachment of first rib and sternum with old age
• can occur in either fibrous or cartilaginous joint
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III.2.2 Fibrous Joints (Synarthrosis)
• fibrous joint, synarthrosis, or synarthrodial joint – a
point at which adjacent bones are bound by collagen fibers
that emerge from one bone, cross the space between them,
and penetrate into the other
• three kinds of fibrous joints
– sutures
– gomphoses
– syndesmoses
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• sutures - immovable or slightly movable fibrous joints that
closely bind the bones of the skull to each other
Wood
Dovetail joint Miter joint Butt joint
Bone
Serrate suture Lap suture Plane suture
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• gomphosis - attachment of a tooth to its socket
• syndesmosis – a fibrous joint at which two bones are
bound by longer collagenous fibers than in a suture or
gomphosis giving the bones more mobility
Gomphosis
Fibrous connective tissue
Syndesmosis
tibia to fibula
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III.2.3 Cartilaginous Joints
• cartilaginous joint, amphiarthrosis or amphiarthrodial
joint – two bones are linked by cartilage
• two types of cartilaginous joints
– synchondroses- bones are bound by hyaline cartilage
• first rib attachment to sternum
– symphyses- two bones joined by fibrocartilage
• pubic symphysis in which right and left pubic bones
joined by interpubic disc
• bodies of vertebrae and intervertebral discs
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III.2.3 Cartilaginous Joints
Pubic symphysis
Body of vertebra
Interpubic disc
(fibrocartilage)
Intervertebral
disc (fibrocartilage)
Clavicle
Rib 1
Sternum
Costal cartilage
synchondroses joint
symphyses joint
symphyses joint
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III.2.4 Synovial Joint
• synovial joint, diarthrosis or diarthrodial joint – joint in
which two bones are separated by a space called a joint
cavity
• synovial joints are classified as:
• plane
• saddle
• hinge
• pivot
• ball and socket
• condyloid
• ellipsoid
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• Accessory Structures for Synovial Joint
• Cartilages
• Fat pads
• Ligaments
• Tendons
• Bursae
Synovial membrane
Intracapsular ligament
Joint capsule
Meniscus
Femur
Tibia
Quadriceps tendon
Patella
Articular cartilage
Fat pad
Patellar ligament
Joint cavity
Meniscus
Bursa
Knee joint, sagittal section
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• plane joint – the joint
surfaces are flat, or at least
relatively flat, and of
approximately equal extent.
• the movement possible is
either a single gliding or
twisting of one bone against
the other, usually within
narrow limits.
• An example is the acromio-
clavicular joint.
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• saddle joint – the two
surfaces are reciprocally
concavoconvex, as a rider
sitting on a saddle.
• the principal movements
possible at the joint occur
about two mutually
perpendicular axes.
• the best example is the
carpometacarpal joint of the
thumb.
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• hinge joint – the surfaces
are so arranged as to allow
movement about one axis
only. In addition the joint is
supported by strong collateral
ligaments.
• the elbow is a typical hinge
joint. The knee joint is
considered to be a modified
hinge joint, as it permits
some movement about a
second axis.
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• pivot joint – movement
occurs about a single axis,
with the articular surfaces
arranged so that one bone
rotates within a fibro-osseous
ring.
• the atlantoaxial joint is a
good example of a pivot joint.
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• ball and socket joint – as
the name suggests the ‘ball’
of one bone fits into the
‘socket’ of the other.
• this type of joint allows
movement about three
principal mutually perpend-
icular axes.
• the hip joint is a ball and
socket joint.
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• condyloid joint – this is a
modified form of a ball and
socket joint, which only
allows active movement to
occur about two perpend-
icular axes.
• however, passive movement
may occur about the third
axis.
• the metacarpophalangeal
joints are examples of such
joints.
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• ellipsoid joint – this is
another form of a ball and
socket joint, although in this
case the surfaces are
ellipsoid in nature.
• movement is only possible
about two perpendicular
axes.
• the radiocarpal joint is an
ellipsoid joint.
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III.3 Movement of Synovial Joint
• vocabulary of movements of synovial joints used in
kinesiology, physical therapy, and other medical fields
– many presented in pairs with opposite or contrasting
meanings
– need to understand anatomical planes and directional
terms
• zero position – the position of a joint when a person is in
the standard anatomical position
– joint movement are described as deviating from the zero
position or returning to it
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Section summary
Terminology
• Specific terms are used to describe
the relationship of one body
part/segment/region to another and
are considered in relation to the
anatomical position of the body.
• The anatomical position is: standing
erect facing forwards, legs together
toes pointing forwards, arms at the
side and palms facing forwards.
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• flexion – movement that
decreases the a joint angle
– common in hinge joints
• extension – movement that
straightens a joint and
generally returns a body
part to the zero position
• hyperextension – further
extension of a joint beyond
the zero position
Extension
Flexion
Extension
Flexion
Hyperextension
© The McGraw-Hill Companies, Inc./Timothy L. Vacula, photographer
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Flexion
Hyperextension
Hip
flexion
Knee
flexion
Extension
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• abduction - movement of a body part in the frontal plane
away from the midline of the body
– hyperabduction – raise arm over back or front of head
• adduction - movement in the frontal plane back toward the
midline
– hyperadduction – crossing fingers, crossing ankles
Abduction Adduction
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Elevation Depression
• elevation - a movement that raises a body part vertically
in the frontal plane
• depression – lowers a body part in the same plane
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• protraction – the anterior
movement of a body part in
the transverse (horizontal)
plane
• retraction – posterior
movement
Protraction
Retraction
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• circumduction - one end of
an appendage remains
stationary while the other
end makes a circular motion
• sequence of flexion,
abduction, extension and
adduction movements
– baseball player winding
up for a pitch
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• rotation – movement in
which a bone spins on its
longitudinal axis
– rotation of trunk, thigh,
head or arm
• medial (internal) rotation
turns the bone inwards
• lateral (external) rotation
turns the bone outwards
Lateral (external) rotationMedial (internal) rotation
Page  70
• supination – forearm
movement that turns the
palm to face anteriorly or
upward
• pronation – forearm
movement that turns the
palm to face posteriorly or
downward
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction
or display.
Supination Pronation
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36
Page  71
Flexion Hyperextension Lateral flexion
flexion, hyperextension, and lateral flexion of vertebral column
Page  72
right and left rotation of trunk
right and left rotation of head
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72

37
Page  73
• lateral excursion – right or
left movement from the zero
position
• medial excursion -
movement back to the
median, zero position
– side-to-side grinding
during chewing
(a) Protraction (b) Retraction
(c) Lateral excursion (d) Medial excursion
Page  74
• ulnar flexion – tilts the hand
toward the little finger
• radial flexion – tilts the hand
toward the thumb
• flexion of fingers – curling them
• extension of fingers –
straightening them
• abduction of the fingers –
spread them apart
• adduction of the fingers – bring
them together again
• flexion of thumb – tip of thumb
directed toward palm
• extension of thumb –
straightening the thumb
• radial abduction – move thumb
away from index finger 90°
• palmar abduction – moves
thumb away from hand and points
it anteriorly
• adduction of thumb – moves it
to the zero position
• opposition – move the thumb to
touch the tips of any of the fingers
• reposition – return the thumb to
the zero position
73
74

38
Page  75
(a) Radial flexion (b) Ulnar flexion
(d) Palmar abduction of thumb (e) Opposition of thumb
(c) Abduction of fingers
Page  76
Dorsiflexion
Zero
position
(c) Eversion(b) Inversion
Plantar flexion
(a) Flexion of ankle
• dorsiflexion – elevation of the toes as you do while swinging the foot
forward to take a step (heel strike)
• plantar flexion - extension of the foot so that the toes point downward
as in standing on tiptoe (toe-off)
• inversion - a movement in which the soles are turned medially
• eversion - a movement in which the soles are turned laterally
• supination of foot – complex combination of plantar flexion, inversion,
and adduction
• pronation of foot – complex combination of dorsiflexion, eversion, and
abduction
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Dr. Ali Selk Ghafari: Biomechanics of Musculoskeletal System: Components of the Musculoskeletal System

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