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Arthrology
Chapter 9
Arthrology Is…
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Study of joints
Joints are defined as places where
the rigid elements of the skeleton
meet.
HOWEVER, joints can be between
the “soft” parts of the skeleton.
Classification of Joints
2 Methods of Classification
Functional Classification
*focuses on the amount of
movement
allowed.
Structural Classification
*focuses on the material that binds
the joint together.
ARTHROLOGY
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Types of Joints
1. SYNOSTOSIS
- called a synarthrosis or
syndesmosis
- is a bone to bone union
- begins as a joint where there is a
fibrous membrane between the two
bones. They are sometimes called
FIBROUS JOINTS or LIGAMENTOUS
UNIONS.
- These are NON-MOVEABLE
- Fontanelles are examples
2.
AMPHIARTHROSIS (cartilagenous
joints)
- moveable and immoveable
- cartilage between two bones
- these joints allow some
movement while still providing
protection.
3.
DIARTHROSIS (synovial joints)
- allow for free movement
- have three characteristics:
1. synovial membrane
- a serous membrane that
produces synovial fluid which reduces
friction and absorbs shock.
2. articular cartilage
3. capsule
-dense connective tissue
covering the joint
Summary of Joint Classes
Structural Class
Fibrous
Cartilaginous
Characteristics
Bones united by
collagen fibers
Bone ends united by
cartilage
Types
1.
2.
3.
1.
2.
Synovial
Bone ends covered with
articular cartilage and
enclosed within a
capsule lined with a
synovial membrane
1.
2.
3.
4.
5.
6.
Suture
Syndesmosis
gomphosis
Mobility
1.
3.
Immobile
(synarthrosis)
Slightly moveable
(amphiarthrosis)
Immobile
Synchondrosis
(hyaline)
Symphysis
(fibrocartliage)
1.
2.
Immobile
Slightly moveable
Plane
Hinge
Pivot
Condyloid
Saddle
Ball and socket
Freely moveable
(diarthrosis) which depends
on joint design
2.
The synovial fluid helps reduce
friction, disipate heat, and absorb
shock.
The articular cartilage acts similarly to
“teflon”, which helps reduce friction
and pressure.
The joint capsule covers and protects
the synovial membrane.
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There are several ligaments that help
hold the portions of the joint
together.
Intracapuslar Ligament – hold the
bones together. Not found in every
joint.
Extracapsular Ligament – called the
collateral ligament. It is a single
band that is actually a thickening of
the joint capsule.
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The synovial membrane is 3-dimensional, like a
knee support enclosing the entire joint. It is NOT
found between the bones. It produces the
synovial fluid.
BURSAE are found between the muscle and
tendons and the bone/joint. These are fluid filled
sacs that reduce friction. In some cases they are
extensions of the synovial sac. When they
become tubular, they can envelope the tendons
and become a SYNOVIAL SHEATH. When these
bursa become dry, friction and inflammation
result, causing BURSITIS.
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We can increase the surface area of
a joint by having a MENISCUS. The
knee has this sort of anatomy.
This type of cartilage can be torn by
torque. Meniscal cartilage cannot
heal itself.
How Do Muscles Act on Bones?
Flexion vs. Extension
Dorsiflexion vs. Plantarflexion
Abduction vs. Adduction
Circumduction
Rotation
Pronation vs. Supination
Protraction vs. Retraction
Elevation vs. Depression
Inversion vs. Eversion
Types of Joints (Articulations)
1.
2.
Ball and Socket Joint
- allow for the most freedom of movement
- triaxial movement – flexion, extension,
abduction, adduction, circumflexion, and
rotation
Hinge Joint
- uniaxial – allows movement in only one
direction. Back and Forth
- allows only flexion and extension in one
plane (sagittal)
- many times the articular surfaces will have
a distinct shape (ie: spool shaped trochlear
surface of the humerus)
3.
4.
Pivot Joint
- allows rotation (uniaxial)
- rounded, pointed, or conical surface on one
bone that fits into a ring of bone on another.
Saddle Joint
- biaxial
- allows flexion, extension, abduction,
adduction, and circumduction.
- surfaces are inverted relative to each other.
5.
Condyloid Joint
- biaxial
- one bone is concave
(hollowed out depression) and the
other is convex (rounded or
elliptical).
- allows flexion, extension,
abduction, and adduction.
- NO ROTATION
6.
7.
Sliding or Gliding Joint
- biaxial
- side to side, back and forth
- two flat surfaces that slide over each other
- NO ANGULAR MOTION
Tongue and Groove (Mortise and Tenon)
- uniaxial
- one side is a slot, the other side is an
extension that fits into the slot.
- NO SIDE TO SIDE MOVEMENT
- Allows flexion and extension
Introduction to Myology and Movement
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Human motion and walking is due
to a system of levers that are made
from bones and muscles.
A lever has a fulcrum, or pivot
point; a force, or energy that has
to be applied; and a resistance, or
opposition to movement.
A wheel is a lever with the pivot in
the center.
3 Types of Human Levers Systems
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Class 1: Fulcrum is between the
force and load.
Force
load
fulcrum
This type of lever pulls our head into an extended position once flexed.
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Class 2: The load is between the
force and fulcrum.
The muscles that elevate us to our tip toes – plantarflexion of the foot on the leg.
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Class 3 Lever
The load is opposite the fulcrum.
Examples of this type of
lever are muscles that move
the forearm.
Requirements For Movement
1.
2.
3.
An alive muscle
A stimulus
- nerve impulse
At least 2 bones
- diarthrosis
- the joint must allow for movement in
plane that the muscle shortens.
- the muscle must be able to pull the
load
- force must be greater than the
resistance
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Muscles that stabilize a limb so it can
move is a FIXATOR.
For example, the trapezius stabilizes the
clavicle and scapula so we can move the
arm but not have the head of the
humerus become deflected in any
direction.
A muscle that provides most of the force
for a particular movement is the PRIME
MOVER. For example, the deltoid is the
prime flexor of the arm on the shoulder.
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Muscle pairs must work together:
AGONIST – assists movement
ANTAGONIST – resists movement
For example: The triceps surae (gastrocnemius and
soleus complex) plantarflexes the foot on the leg.
This is the plantarflexory agonist. The muscles
that work against the triceps are the dorsiflexory
muscles (tibialis anterior and long extensors).
The opposite is also true: The plantarflexors are the
antagonists to the dorsiflexors.
SYNOVIAL JOINTS
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Occurs at ends of bones
Articular cartilage enclosed within an
articular capsule and lined with a synovial
membrane.
All freely moveable (diarthrosis)
Type of movement depends on the shape
and design of the joint.
6 Types
1. Plane
4. Condyloid
2. Hinge
5. Saddle
3. Pivot
6. Ball and Socket
Part of a Synovial Joint
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Joint Cavity – fluid filled potential space.
Articulating surfaces:
simple joint – 2 articulating surfaces
compound joint - >2 articular surfaces
Articular Cartilage – hyaline cartilage. Spongy
cushions absorb compression
Articular Capsule
2 layers:
1. fibrous capsule – outside, dense irregular
CT that is continuous with the periosteum.
2. synovial membrane – loose CT. Makes
synovial fluid for protection.
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Synovial Fluid
*viscous fluid resembling raw egg whites.
*filtrate of blood
*contains glycoproteins
Reinforcing Ligaments
*bands that hold the joint together.
*Extracapsular – outside the capsule
*Intracapsular – internal to the capsule
Neurovascular Bundle
*Nerves and Blood Vessels
*Detect pain when joint is disrupted (ie:
sprains,
dislocations)
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Synovial joints have lubricating devices to
allow the bones to move across one
another with minimal friction.
Synovial joints are subject to
compression. Compression occurs when
muscles that hold the bones together
contract.
Lubricating fluid is squeezed out of the
joint onto the opposing surfaces. When
pressure on the joint ceases, the fluid
rushes back into the articular cartilage.
The fluid is absorbed back into the
cartilage ready for the next compressive
force. This is called weeping lubrication.
MOVEMENTS OF
SYNOVIAL JOINTS
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Movement caused by muscular
contraction.
3 Types of Movments:
1. Gliding – sliding of flat surfaces
across each other. Found mainly between
the carpals and between the tarsals.
2. Angular – increase or decreases the
angle between the two bones
3. Rotation – movement of bone
around its long axis.
SYNOVIAL JOINTS ARE CLASSIFIED
BY SHAPE
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The shapes of the articulating surfaces determine
the movement allowed at a joint.
Types of synovial joints:
1. plane – flat articular surfaces. Short gliding
movements are allowed.
2. hinge – cylindrical end of one bone fits into
the trough of another bone. Angular movement is
in one plane. Uniaxial joint along one plane.
3. pivot – rounded end of one fits into a ring
formed by another bone.
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4. Condyloid – egg shaped articular
surface fits into the oval concavity
in another.
5. Saddle Joint – has both convex
and concave areas.
6. Ball and Socket – spherical head
of one bone fits into a round socket
in another.
Disorders of Joints
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Injury
1. Sprain
- stretching or tearing of a
ligament
2. Dislocation
- joint alignment is interrupted
- Subluxation is a partial or
incomplete dislocation of a
joint.
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1.
2.
Inflammatory Conditions
Bursitis
- inflammation of a bursa
- Bursae are sacs of fluid that
serve to
protect boney prominences.
Tendinitis
- inflammation of a tendon
sheath
3.
4.
Osteoarthritis
- most common type of arthritis
- degenerative condition of the
articular cartilage
- Enzymes wear down the cartilage
matrix due to “wear and tear”
Rheumatoid Arthritis
- inflammation of the synovium
- autoimmune in origin
- often results in ankylosis of the
joint