Honors Anatomy & Physiology
Chapter 8
JOINTS

aka Articulations
2 Functions:
1. Hold Bones Together
2. Allows otherwise rigid skeleton to have
some flexibility

Classification of Joints
 Functionally
 Structurally
 Named
 Named
according
to how much
movement
allowed @ joint
according
to presence of
fibrous tissue,
cartilage, or a
joint cavity
separate the
articulated bones
Functional Joints

Synarthrosis
 Immovable joints
 Skull bones

Amphiarthrosis
 Slightly movable joints
Symphysis pubis
 Diarthrosis

 Freely movable joints
 Ball & Socket or Hinge Joints
Structural Joints
Fibrous Joints
1.


Bones united by fibrous tissue
Joint connecting distal tibia & fibula
Cartilaginous Joints
2.


Bone ends connected by cartilage
Pubic symphysis
Synovial Joints
3.

Articulating ends of bone separated by joint
cavity
4 Features of Synovial Joints
Articular Cartilage
1.

Hyaline cartilage covers ends of bones
Fibrous Articular Capsule
2.


Joint surfaces enclosed by capsule of fibrous CT
Capsule lined by synovial membrane
Joint Cavity
3.

Contains synovial fluid
Reinforcing Ligaments
4.

Reinforce fibrous articular capsule
General Structure
of a
Synovial Joint
Articular Cartilage
 Joint Cavity
 Articular Capsule
 Synovial Fluid
 Reinforcing Ligaments
 Nerves & Blood Vessels
 Some also have: menisci, bursae, tendon
sheaths outside the joint proper

Factors Influencing Stability
of Synovial Joints
Joints must be stabilized to avoid
dislocation
 Stability of a joint depends on 3 factors:
1. Articular surfaces: overall minor role
2. Ligaments: prevent excessive or
undesirable motion at the joint
3. Muscle tone: muscle tendons that cross
the joint most stabilizing factor

Types of Synovial Joints
PLANE JOINT
1.



Articular surfaces flat
Allow gliding movement (w/out rotation)
Example: intercarpal joints of wrist & ankle
Types of Synovial Joints
2. HINGE JOINT

cylindrical end of bone fits into
trough-shaped surface of another bone
 Angular movement allowed in 1 plane
 Examples: elbow, knee, interphalangeal
joints
Types of Synovial Joints
3. PIVOT JOINT
 Rounded end of 1 bone fits into sleeve or
ring of another bone
 allows 1 bone to rotate along its long axis
 Example: joint between atlas & dens of axis
Types of Synovial Joints
4.CONDYLOID JOINT
 “knuckle-like”
 Egg-shaped end of 1 bone fits into oval concavity
in another bone
 Allows for moving bone to travel side-to-side &
back-and-forth but cannot rotate along its long
axis
 Example: metacarpophalangeal joint
4. CONDYLOID JOINT
Types of Synovial Joints
5. SADDLE JOINTS
 Each articular surface has convex &
concave areas
 Same movements as condyloid joints
 Example: twiddling your thumbs
Types of Synovial Joints
6. BALL & SOCKET JOINTS
 Spherical head of 1 bone fits into a round
socket formed by 1 or more bones
 Allows movement is 3 dimensions(most
freely moving of synovial joints)
Types of Movements
@
Synovial Joints
1. Gliding
 relatively flat surfaces move back-and-forth &
side-to-side

Types of Movements
@
Synovial Joints
2. flexion/extension/ hyperextension:
 opposite movements

 flexion: decrease in angle between articulating
bones
 extension: increase in angle between articulating
bones
 hyperextension: continuation of extension beyond
the anatomical position
Types of Movements
@
Synovial Joints

3. abduction/adduction/ circumduction
 abduction: movement of bone away from midline
 adduction: movement of bone toward midline
 circumduction: movement of distal end of a body
part in a circle
Types of Movements
@
Synovial Joints
4. elevation/depression:
 elevation: upward movement of part of body
(closing mouth, shrugging shoulders)
 depression: downward movement of part of
body (opening mouth, returning elevated
shrugged shoulders to anatomical position)

Types of Movements
@
Synovial Joints
5. protraction/retraction
 protraction: movement of part of body
anteriorly in transverse plane
 retraction: returning a protracted part of body
to anatomical position

Types of Movements
@
Synovial Joints
6. inversion/ eversion
 inversion: movement of soles medially @
intertarsal joints (soles face each other)
 eversion: movement of soles laterally @
intertarsal joints

Types of Movements
@
Synovial Joints
7. dorsiflexion/ plantar flexion
 dorsiflexion: bending foot @ ankle in direction
of dorsum (superior surface)
 plantar flexion: bending foot @ ankle in
direction of plantar surface

Types of Movements
@
Synovial Joints
8. supination/pronation
 supination: movement of forearm in which
palm is turned anteriorly
 pronation: movement of forearm in which
distal end of radius crosses over distal end
ulna & palm is turned posteriorly

Types of Movements
@
Synovial Joints
9. opposition
 movement of thumb in which thumb moves
across palm to touch tips of the fingers on
same hand

Ball - & - Socket Joint
ball-like surface of one bone fits into a cuplike
depression of another bone
 permits movement around 3 axis + all
directions in between

 flexion
 extension
 abduction
 adduction
 circumduction
 rotation
SPRAINS
Ligaments or tendons reinforcing a joint
are damaged by excessive stretching or
tearing
 Both have poor blood supply so heal slowly

ARTHRITIS
“inflammation of a joint”
 General term for >100 different diseases
 Most wide-spread, disabling disease in USA
 Onset: same symptoms: joint stiffness &
swelling
 Synovial membrane inflammed  thickens 
less synovial fluid  increased friction

Rheumatoid Arthritis
Autoimmune disorder
 Adult onset or Juvenile onset
 Women 3x more often than men
 Any synovial joint could be affected, often
symmetrical involvement
 disfiguring

Rheumatoid Arthritis
Osteoarthritis
Most common form of arthritis
 Chronic degenerative condition: “wear-andtear”
 Affects articular cartilage (eventually
breaks down)  increased friction  bone
spurs develop  restricts movement

Osteoarthritis