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Chapter 9
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Joints
 Joints



and their classification
bony joints
fibrous joints
cartilaginous joints
 Synovial
joints
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Joints and Their Classification
 Arthrology
= study of the joints
 Kinesiology = study of musculoskeletal
movement
 Classified by freedom of movement



diarthrosis (freely movable)
amphiarthrosis (slightly movable)
synarthrosis (little or no movement)
 Classified

how adjacent bones are joined
fibrous, cartilaginous, bony or synovial
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Bony Joint (Synostosis)
 Gap



between two bones ossifies
frontal and mandibular bones in infants
cranial sutures in elderly
attachment of first rib and sternum
 Can
occur in either fibrous or cartilaginous
joint
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Fibrous Joints (Synarthrosis)
 Collagen
fibers span the space
between bones

sutures, gomphoses and syndesmoses
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Fibrous Joint -- Sutures

Immovable fibrous joints

bind skull bones together

Lap - overlapping beveled edges

Plane - straight, nonoverlapping
edges

palatine processes of the maxillae
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Types of Sutures
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Fibrous Joint -- Gomphoses
 Attachment
of a tooth to its
socket
 Held in place by fibrous
periodontal ligament

collagen fibers attach
tooth to jawbone
 Some
movement while
chewing
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Fibrous Joint -- Syndesmosis
 Two
bones bound
by ligament only

interosseus
membrane
 Most
movable of fibrous joints
 Interosseus membranes unite radius to ulna
and tibia to fibula
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Cartilaginous Joint -- Synchondrosis
 Bones
are joined by
hyaline cartilage


rib attachment to
sternum
epiphyseal plate in
children binds
epiphysis and
diaphysis
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Cartilaginous Joint -- Symphysis
2
bones joined by
fibrocartilage

pubic symphysis
and intervertebral
discs
 Only
slight amount
of movement is
possible
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Synovial Joint

Joint in which two bones are separated by a
space called a joint cavity
 Most are freely movable
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General Anatomy

Articular capsule encloses joint cavity


continuous with periosteum
lined by synovial membrane

Synovial fluid = slippery fluid; feeds cartilages
 Articular cartilage = hyaline cartilage covering the joint
surfaces
 Articular discs and menisci




jaw, wrist, sternoclavicular and knee joints
absorbs shock, guides bone movements and distributes forces
Tendon attaches muscle to bone
Ligament attaches bone to bone
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Tendon Sheaths and Bursae

Bursa = saclike extension of joint capsule


between nearby structures so slide more easily past each other
Tendon sheaths = cylinders of connective tissue lined with
synovial membrane and wrapped around a tendon
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Components of a Lever
 A lever
is a rigid object that rotates around a
fixed point called a fulcrum
 Rotation occurs when effort overcomes
resistance

resistance arm and effort arm are described
relative to fulcrum
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Mechanical Advantage of a Lever
 Two

kinds of levers
lever that helps increase output of force
• human moving a heavy object with help of crowbar

lever move object further and faster
• movement of row boat with paddle
 Types
of levers produce either increase in
speed or force
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First-Class Lever


Has fulcrum in the middle between effort and resistance
Atlantooccipital joint lies between the muscles on the back of
the neck and the weight of the face

loss of muscle tone occurs when you nod off in class
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Second-Class Lever

Resistance between fulcrum and effort
 Resistance from the muscle tone of the temporalis
muscle lies between the jaw joint and the pull of the
diagastric muscle on the chin as it opens the mouth
quickly
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Third-Class Lever

Effort between the resistance and the fulcrum


most joints of the body
The effort applied by the biceps muscle is applied to
the forearm between the elbow joint and the weight of
the hand and the forearm
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Range of Motion
 Degrees
through which a joint can move
 Determined by


structure of the articular surfaces
strength and tautness of ligaments, tendons and
capsule
• stretching of ligaments increases range of motion
• double-jointed people have long or slack ligaments

action of the muscles and tendons
• nervous system monitors joint position and muscle
tone
20
Axes of Rotation

Shoulder joint has 3 degrees of freedom =
multiaxial joint
 Other joints – monoaxial or biaxial
21
Types of Synovial Joints
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Ball-and-Socket Joints
 Smooth
hemispherical head fits within a
cuplike depression


head of humerus into glenoid cavity of
scapula
head of femur into acetabulum of hip bone
 Multiaxial
joint
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Condyloid (ellipsoid) Joints
 Oval
convex surface on one bone fits into
a similarly shaped depression on the next


radiocarpal joint of the wrist
metacarpophalangeal joints at the bases of
the fingers
 Biaxial
joints
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Saddle Joints
 Each
articular surface is shaped like a
saddle, concave in one direction and convex
in the other

trapeziometacarpal joint at the base of the
thumb
 Biaxial

joint
more movable than a condyloid or hinge joint
forming the primate opposable thumb
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Gliding Joints
 Flat
articular surfaces in which bones slide
over each other
 Limited monoaxial joint
 Considered amphiarthroses
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Hinge Joints
 One
bone with convex surface that fits into
a concave depression on other bone



ulna and humerus at elbow joint
femur and tibia at knee joint
finger and toe joints
 Monoaxial
joint
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Pivot Joints
 One
bone has a projection that fits into a
ringlike ligament of another
 First bone rotates on its longitudinal axis
relative to the other


atlantoaxial joint (dens and atlas)
proximal radioulnar joint allows the radius during
pronation and supination
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Flexion, Extension and Hyperextension
 Flexion
decreases the
angle of a joint
 Extension straightens
and returns to the
anatomical position
 Hyperextension =
extension beyond 180
degrees
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Flexion, Extension and Hyperextension
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Abduction and Adduction

Abduction is movement of a part away from the
midline


hyperabduction – raise arm over back or front of head
Adduction is movement towards the midline

hyperadduction – crossing fingers
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Elevation and Depression

Elevation is a movement that raises a bone vertically


mandibles are elevated during biting and clavicles during
a shrug
Depression is lowering the mandible or the
shoulders
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Protraction and Retraction
 Protraction
= movement
anteriorly on horizontal
plane

thrusting the jaw
forward, shoulders or
pelvis forward
 Retraction
is movement
posteriorly
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Circumduction

Movement in which 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
on
longitudinal axis

rotation of trunk,
thigh, head or arm
 Medial
rotation
turns the bone
inwards
 Lateral rotation
turns the bone
outwards
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Supination and Pronation

In the forearm and foot
 Supination



rotation of forearm so that the
palm faces forward
inversion and abduction of foot
(raising the medial edge of the
foot)
Pronation


rotation of forearm so the palm
faces to the rear
eversion and abduction of foot
(raising the lateral edge of the
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foot)
Movements of Head and Trunk

Flexion, hyperextension and lateral flexion of
vertebral column
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Rotation of Trunk and Head

Right rotation of trunk; rotation of head
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Movements of Mandible

Lateral excursion = sideways movement
 Medial excursion = movement back to the
midline


side-to-side grinding during chewing
Protraction – retraction of mandible
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Movement of Hand and Digits

Radial and ulnar
flexion
 Abduction of fingers
and thumb
 Opposition is
movement of the
thumb to approach
or touch the
fingertips
 Reposition is
movement back to
the anatomical
position
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Movements of the Foot




Dorsiflexion is raising of the toes as when you swing the
foot forward to take a step (heel strike)
Plantarflexion is extension of the foot so that the toes point
downward as in standing on tiptoe
Inversion is a movement in which the soles are turned
medially
Eversion is a turning of the soles to face laterally
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The Humeroscapular Joint




Most freely movable joint in the body
 shallowness and looseness
 deepened by glenoid labrum
Supported by ligaments and tendons
 3 glenohumeral, coracohumeral,
transverse humeral and biceps tendon
are
important joint stabilizer
Supported by rotator cuff musculature
 tendons fuse to joint capsule and
strengthens it
 supraspinatus, infraspinatus, teres
minor and subscapularis,
4 Bursae associated with shoulder joint
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Stabilizers of the Shoulder Joint
43
Tendons of Rotator Cuff
Muscles
44
The Elbow Joint
 Single
joint capsule
enclosing the
humeroulnar and
humeroradial joints
 Humeroulnar joint is
supported by collateral
ligaments.
 Radioulnar joint is head
of radius held in place
by the anular ligament
encircling the head
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Elbow Joint
46
The Coaxal (hip) Joint

Head of femur articulates with acetabulum
 Socket deepened by acetabular labrum
 Blood supply to head of femur found in ligament of
the head of the femur Joint capsule strengthened by
ligaments
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Hip Joint

Joint capsule
strengthened by
ligaments



pubofemoral
ischiofemoral
iliofemoral
48
Dissection of Hip Joint
49
The Knee Joint

Most complex diarthrosis


patellofemoral = gliding joint
tibiofemoral = gliding with slight
rotation and gliding possible in
flexed position

Joint capsule anteriorly consists
of patella and extensions of
quadriceps
femoris tendon
 Capsule strengthened by
extracapsular and intracapsular
ligaments
50
Knee Joint – Sagittal Section
51
Knee Joint – Anterior and Posterior
Views

Anterior and lateral cruciate ligaments limit
anterior and posterior sliding movements
 Medial and lateral collateral ligaments prevent
rotation of extended knee
52
Knee Joint – Superior View

Medial and lateral meniscus absorb shock and
shape joint
53
Dissection of Knee Joint
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Arthritis
 Arthritis
is a broad term for pain and
inflammation
 Osteoarthritis results from years of joint wear



articular cartilage softens and degenerates
accompanied by crackling sounds called
crepitus
bone spurs develop on exposed bone tissue
causing pain
55
Arthritis and Artificial Joints
 Rheumatoid
arthritis is autoimmune attack
on joint


antibodies attack synovial membrane,
enzymes in synovial fluid degrade the
cartilage, bones ossify
remissions occur, steroids and aspirin control
inflammation
 Arthroplasty
is replacement of diseased
joint with artificial device called prosthesis
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Rheumatoid Arthritis
57
Joint Prostheses
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