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Chapter 9
Lecture
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Joints
• Joints and their classification
– bony joints
– fibrous joints
– cartilaginous joints
• Synovial joints
• Anatomy of selected diarthroses
– humeroscapular joint
– elbow joint
– coxal joint
– knee joint
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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
• Serrate - interlocking lines
– coronal, sagittal and lambdoid
sutures
• Lap - overlapping beveled
edges
– temporal and parietal bones
• 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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Mechanical Advantage
• Mechanical advantage is calculated from the
length of the effort arm divided by the length of
the resistance arm
• Contraction of the biceps muscle causes the
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hand to move fast and further (MA <1.0)
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
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Axes of Rotation
• Shoulder joint has 3 degrees of freedom =
multiaxial joint
• Other joints – monoaxial or biaxial
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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
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vertebral column
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
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• Eversion is a turning of the soles to face laterally
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
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Tendons of Rotator Cuff
Muscles
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Dissection of Shoulder Joint
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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
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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
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Dissection of Hip Joint
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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
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Knee Joint – Sagittal Section
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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
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Knee Joint – Superior View
• Medial and lateral meniscus absorb shock
and shape joint
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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
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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
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Joint Prostheses
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