Joints (Articulations)
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Weakest parts of the skeleton
Articulation – site where two or more bones
meet
Functions of joints
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Give the skeleton mobility
Hold the skeleton together
Classification of Joints:
Structural
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Structural classification focuses on the
material binding bones together and whether or
not a joint cavity is present
The three structural classifications are:
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Fibrous
Cartilaginous
Synovial
Classification of Joints:
Functional
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Functional classification is based on the
amount of movement allowed by the joint
The three functional classes of joints are:
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Synarthroses – immovable
Amphiarthroses – slightly movable
Diarthroses – freely movable
Fibrous Structural Joints
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The bones are joined by fibrous tissues
There is no joint cavity
Most are immovable
There are three types – sutures, syndesmoses,
and gomphoses
Fibrous Structural Joints:
Sutures
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Occur between the bones of the skull
Comprised of interlocking junctions
completely filled with connective tissue fibers
Bind bones tightly together, but allow for
growth during youth
In middle age, skull bones fuse and are called
synostoses
Fibrous Structural Joints: Sutures
Figure 8.1a
Fibrous Structural Joints:
Syndesmoses
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Bones are connected by a fibrous tissue
ligament
Movement varies from immovable to slightly
variable
Examples include the connection between the
tibia and fibula, and the radius and ulna
Fibrous Structural Joints:
Syndesmoses
Figure 8.1b
Fibrous Structural Joints:
Gomphoses
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The peg-in-socket fibrous joint between a
tooth and its alveolar socket
The fibrous connection is the periodontal
ligament
Cartilaginous Joints
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Articulating bones are united by cartilage
Lack a joint cavity
Two types – synchondroses and symphyses
Cartilaginous Joints:
Synchondroses
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A bar or plate of hyaline cartilage unites the
bones
All synchondroses are synarthrotic
Examples include:
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Epiphyseal plates of children
Joint between the costal cartilage of the first rib
and the sternum
Cartilaginous Joints: Symphyses
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Hyaline cartilage covers the articulating
surface of the bone and is fused to an
intervening pad of fibrocartilage
Amphiarthrotic joints designed for strength
and flexibility
Examples include intervertebral joints and the
pubic symphysis of the pelvis
Synovial Joints
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Those joints in which the articulating bones
are separated by a fluid-containing joint cavity
All are freely movable diarthroses
Examples – all limb joints, and most joints of
the body
Synovial Joints: General
Structure
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Synovial joints all have the following
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Articular cartilage
Joint (synovial) cavity
Articular capsule
Synovial fluid
Reinforcing ligaments
Synovial Joints: General
Structure
Figure 8.3a, b
Synovial Joints: FrictionReducing Structures
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Bursae – flattened, fibrous sacs lined with
synovial membranes and containing synovial
fluid
Common where ligaments, muscles, skin,
tendons, or bones rub together
Tendon sheath – elongated bursa that wraps
completely around a tendon
Synovial Joints: FrictionReducing Structures
Figure 8.4
Synovial Joints: Stability
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Stability is determined by:
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Articular surfaces – shape determines what
movements are possible
Ligaments – unite bones and prevent excessive or
undesirable motion
Synovial Joints: Stability
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Muscle tone is accomplished by:
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Muscle tendons across joints acting as stabilizing
factors
Tendons that are kept tight at all times by muscle
tone
Synovial Joints: Movement
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The two muscle attachments across a joint are:
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Origin – attachment to the immovable bone
Insertion – attachment to the movable bone
Described as movement along transverse,
frontal, or sagittal planes
Synovial Joints: Range of Motion
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Nonaxial – slipping movements only
Uniaxial – movement in one plane
Biaxial – movement in two planes
Multiaxial – movement in or around all three
planes
Gliding Movements
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One flat bone surface glides or slips over
another similar surface
Examples – intercarpal and intertarsal joints,
and between the flat articular processes of the
vertebrae
Angular Movement
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Flexion — bending movement that decreases
the angle of the joint
Extension — reverse of flexion; joint angle is
increased
Dorsiflexion and plantar flexion — up and
down movement of the foot
Angular Movement
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Abduction — movement away from the
midline
Adduction — movement toward the midline
Circumduction — movement describes a cone
in space
Gliding Movement
Figure 8.5a
Angular Movement
Figure 8.5b
Angular Movement
Figure 8.5c, d
Angular Movement
Figure 8.5e, f
Rotation
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The turning of a bone
around its own long
axis
Examples
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Between first two
vertebrae
Hip and shoulder joints
Figure 8.5g
Special Movements
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Supination and pronation
Inversion and eversion
Protraction and retraction
Elevation and depression
Opposition
Special Movements
Figure 8.6a
Special Movements
Figure 8.6b
Special Movements
Figure 8.6c
Special Movements
Figure 8.6d
Special Movements
Figure 8.6e