Chapter 7
Joints
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Chapter 8
Joints of the Skeletal System
• Articulations
- Junctions between bones
• Bind parts of skeletal system together
• Make bone growth possible
• Permit parts of the skeleton to change
shape during childbirth
• Enable body to move in response to
skeletal muscle contraction
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8-2
Joints

Classifications
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Structurally: by their anatomy
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
Fibrous, cartilaginous, or synovial
Functionally: by the degree of movement they
permit

Immovable, slightly movable, and freely movable
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Structural Classification

Based on what is between bones:



Space (or not)
Type of connective tissue present
Types
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Fibrous joints - no cavity, just dense irregular
connective tissue
Cartilaginous joints - no cavity, bones held
together by cartilage
Synovial joints - have synovial cavity, dense
irregular tissue of articular capsule, and often
ligaments
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Functional Classification

Types

Synarthrosis: immovable
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Amphiarthrosis: slightly movable
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Pelvis, sutures, teeth
Epiphyseal plate, tibia-fibula, vertebrae, pelvic symphysis
Diarthrosis: freely movable


Most joints of the body
All diarthrotic joints are synovial
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Fibrous Joints
3 Types
• Syndesmosis
• Suture
• Gomphosis
Syndesmosis
• long fibers
connect bones
• amphiarthrotic
• distal ends of
tibia and fibula
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8-4
Fibrous Joints
Suture
• between flat bones
• synarthrotic
• thin layer of
connective tissue
connects bones
Gomphosis
• cone-shaped bony
process in a socket
• tooth in jawbone
• synarthrotic
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8-5
Fibrous Joints

Interosseous membrane (amphiarthrosis)


Has greater amount of dense irregular
connective tissue
Examples: extensive membranes between shafts
of some long bones


Radius-ulna
Tibia-fibula
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Fibrous Joints
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Fibrous Joints
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Fibrous Joints
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Cartilaginous Joints
Symphysis
• pad of fibrocartilage between
bones
• Compressible “shock absorber”
• amphiarthrotic
•Ex: intervertebral discs &
symphysis pubis
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8-7
Cartilaginous Joints

Synchondrosis (synarthrosis)


Cartilage connects two areas of bone
Example

Epiphyseal (growth) plate connecting epiphysis and
diaphysis of long bone (synarthrosis)
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Cartilaginous Joints
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Cartilaginous Joints
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Synovial Joints: Structure


Synovial cavity: space containing fluid
Articular cartilage


Covers ends of bones, absorbs shock
Articular capsule



Inner layer: synovial membrane that secretes
synovial fluid (reduces friction, supplies nutrients)
Outer layer: dense, irregular connective tissue
diarthrotic
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Synovial Joints: Structure
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Synovial Joints
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8-8
Synovial Joints: Structure

In some cases synovial joints include:

Ligaments (either inside or outside of joint cavity)
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A ligament joins a bone to another bone across a
synovial
Menisci (cartilage discs)
Articular fat pads
Bursae
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Sacs made of synovial membranes containing fluid
Located where friction can occur
Examples: between skin-bone, tendons-bones,
muscles-bones, ligaments-bones
act as “ball bearings”
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General Structure of a Synovial Joint
Synovial fluid = viscous lubricating fluid within
cavity
1.
Reduces friction between cartilages of 2
bones
2.
Provide “weeping lubrication”
3.
Nourish cartilage
4.
Contain phagocytes
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Skeletal Muscle Actions
• origin – immovable end
• insertion – movable end
* When muscle contracts & shortens its insertion is pulled toward its
origin
• prime mover (agonist) – primarily responsible for movement
• synergists – assist prime mover
• antagonist – muscle in opposition to the action of the prime
mover’s and cause movement in the opposite direction
•Antagonist relaxes (stretches) during prime movement
•Fixators – muscle groups that stabilize the origin of the prime
mover so that the prim mover can act more efficiently
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9-30
Types of Movements at Synovial Joints

Gliding
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Flexion
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Decrease in angle between articulating bones
Extension
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Flat bone surfaces moving across each other
Increase in angle between articulating bones
In anatomical position the body is in full extension
Hyperextension

Bending beyond 180o degrees, such as moving
humerus backwards behind anatomical position
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Movements

Abduction
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Adduction
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Movement of bone toward midline
Circumduction

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Movement of bone away from midline
Movement of distal end in a circle
Rotation

Bone revolves around its own longitudinal axis
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Types of Movements at Synovial Joints
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Special Movements

Elevation

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Depression

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Movement downward
Protraction


Movement upward
Movement forward
Retraction

Movement backward into anatomical position
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Special Movements at Synovial Joints
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Special Movements at Synovial Joints
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Special Movements

Inversion
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Eversion
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Move soles laterally
Dorsiflexion

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Move soles medially
Bend foot toward dorsum (“stand on heels”)
Plantar flexion

Bend foot toward plantar surface (“stand on toes”)
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Special Movements at Synovial Joints
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Special Movements at Synovial Joints
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Special Movements at Synovial Joints

Supination

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Movement of forearm so palms face forward or
upward
Pronation

Movement of forearm so palms face backward or
downward
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Special Movements at Synovial Joints
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Types of Synovial Joints

Saddle joints



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One side of saddle-shaped, other like a rider
astride it
Example: trapezium (carpal) to metacarpal-1
(thumb)
Movements: triaxial (F, E, ABD, ADD, ROT)
Ball-and-socket joints


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Ball-like surface into cuplike socket surface
Example: shoulder, hip
Movements: triaxial (F, E, ABD, ADD, CIR, ROT)
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Types of Synovial Joints
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Types of Synovial Joints
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Types of Synovial Joints
Condyloid joints
Convex oval surface to concave
oval surface
Examples: wrist,
metacarpophalangeal-2 to -5
joints
Movements F, E, ABD, ADD
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8-9
Types of Synovial Joints
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Six Types of Synovial Joints

Planar joints
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Articulating surfaces flat or slightly curved
Examples: between carpals, tarsals, sternumclavicle, scapula-clavicle
Movements: gliding
Hinge joints
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Convex-to-concave surfaces
Examples: elbow, knee, ankle, interphalangeal
Movements: flexion (F) and extension (E) only
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Types of Synovial Joints
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8-10
Types of Synovial Joints
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Types of Synovial Joints
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Types of Synovial Joints

Pivot joints
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Rounded surface with ring formed by bone and
ligament
Examples: atlantoaxial joint (to turn head to say
“no”) and radius-ulna for pronation-supination
Movement: rotation (ROT)
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Types of Synovial Joints
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8-11
Types of Synovial Joints
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Details of a Synovial Joint: Knee Joint
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See slides 10a-d
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Ligaments
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Menisci (medial and lateral)
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Tibial and fibular collateral ligaments
Anterior cruciate ligament (ACL): 70 % of knee injuries
Posterior cruciate ligament (PCL)
Fibrocartilage discs that increase stability of knee joint
Bursae
Arthroplasty
Knee replacement: total or partial
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Knee Joint
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Knee Joint
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Knee Joint
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Knee Joint
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Aging of Joints



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Decrease in production of synovial fluid
Thinning of articular cartilage
Ligaments shorten and lose flexibility
Influenced by genetic factors
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Common Disorders of Joints

Common joint injuries
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Rotator cuff injury
Separated shoulder
Tennis elbow
Dislocation of the radial head
Knee injuries: swollen knee, rupture of tibial
collateral ligaments, dislocated knee
Rheumatism: rheumatoid arthritis, osteoarthritis
Ligaments shorten and lose flexibility
Influenced by genetic factors
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Life-Span Changes
• Fontanels of skull harden in first 2 years
• Epiphyseal plates harden from ages 14-20 years
• Fibrocartilage loses water, decreases flexibility of
intervertebral joints and knees
• Collagen changes causes stiffening beginning at age 30
• Joint stiffness is an early sign of aging
• Regular exercise can prevent stiffness
• Fibrous joints first to strengthen over a lifetime
• Changes in symphysis joints of vertebral column
diminish flexibility and decrease height
• Synovial joints lose elasticity
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8-23
Clinical Application
Joint Disorders
Sprains
• damage to cartilage, ligaments, or tendons associated with
joints
• forceful twisting of joint Arthritis
• inflamed, swollen, painful joints
Bursitis
• Rheumatoid Arthritis
• inflammation of a bursa
• Osteoarthritis
• overuse of a joint
• Gout
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8-24
End of Chapter 7

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Copyright 2010, John Wiley & Sons, Inc.