Joint Mechanics
Today’s Agenda
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What is a Joint?
Different Types of Joints
Range of Movement in Joints
Structure and Function of Joints
Characteristics of Synovial Joints
Types of Synovial Joints
Joint Movement
What is a Joint?
• Joints are points of contact (also known as
articulations) between 2 connected bones
• They are part of the musculoskeletal
system
Different Types of Joints
• Joints are classified according to their
structure and function
• There are 3 types of joints:
1. Fibrous
2. Cartilaginous
3. Synovial
Range of Movement in Joints
• There are 3 main types of functional
classifications for range of movement in
joints:
1. synarthrosis – an immovable joint
2. amphiarthrosis – a slightly movable
joint
3. diathrosis – a freely movable joint
Fibrous Joints
• Bound tightly together by connective
tissue and allow no movement
• An example of a fibrous joint are sutures
which are joints between the interlocking
bones of the skull
• Sutures become immobile after birth
(synarthrosis)
Fibrous Joints
Cartilaginous Joints
• Cartilaginous joints are also known as
fibrocartilaginous joints
• The body of one bone connects to the body of
another by cartilage
• Slight movement is possible (amphiarthrosis)
• An example of this is the intervertebral discs –
they have a hard outer disc with a soft core
which allows some movement while protecting
the body against severe jolts such as landing on
one’s feet. The bones that connect your ribs to
your sternum are another example of this.
Cartilaginous Joints
Synovial Joints
• The most common joint in the body
• It allows the most range of movement
• The bony surface of the joint is separated by a
lubricating fluid (the synovia) and by cartilage
• This type of joint is also joined by ligaments,
tough bands of elastic tissue that enclose then
ends of the articulating bones and form the
capsule containing the synovial membrane
• They play a major role in human movement and
the most common places for synovial joints are
at the knee, ankle and shoulder
Synovial Joints
Recap – Structure and Function of
Joints
Structure
Function
Fibrous --------------------- Synarthrosis
Cartilaginous -------------- Amphirarthrosis
Synovial -------------------- Diathrosis
Characteristics of Synovial Joints
• Synovial joints permit movement between 2 or
more bones. They can be distinguished by the
following characteristics:
- articulating cartilage
- the joint capsule
- the joint cavity
- the bursae (pl.) (bursa – sing.)
- intrinsic ligaments
- extrinsic ligaments
Characteristics of Synovial Joints
• Articulating cartilage is located at the ends of the bones
that come into contact with one another. An example is
this hyaline cartilage
• The joint capsule is a fibrous structure that consists of
the synovial membrane and fibrous capsule. They
synovial membrane allows certain nutrients to pass
through while the fibrous capsule keeps the synovial fluid
from leaking.
• The joint cavity is located between the two bony
articulating surfaces. It is filled with synovial fluid which
acts as a lubricant for the joint. It is essential to reducing
friction and providing nutrients for the articulating
cartilage.
Characteristics of Synovial Joints
• The bursae are small, flattened fluid sacs
found at friction points between tendons,
ligaments and bones.
• Intrinsic ligaments are thick bands of
fibrous connective tissue that help thicken
and reinforce the joint capsule.
• Extrinsic ligaments are separate from the
joint capsule. They help reinforce the joint
by attaching the bones together.
Types of Synovial Joints
• Synovial Joints are distinguished by the types of
movement the joint permits.
• There are 6 types of synovial joints:
1. Gliding (Plane or Arthrodial)
2. Hinge (Ginglymus)
3. Pivot (or Trochoid)
4. Ellipsoid
5. Saddle
6. Ball and Socket (Spheroidal)
Gliding Joints
• This joint is also known as a plane or
arthrodial joint
• It allows movement in 1 plane (flexion,
extension)
• This type of joint connects to flat or slightly
curved bone surfaces.
• An example of this joint is the foot
between the tarsals or hand between the
carpals
Hinge Joints
• Hinge joints are also known as ginglymus
joints
• They have a convex portion on one side of
the bone fitting into a concave portion of
another.
• It allows movement in 1 plane (flexion,
extension)
• An example of this joint are the bones of
the fingers (phalanges)
Pivot Joints
• This joint is also known as a trochoid joint
• It allows rotation in one plane – a rounded
point of one bone fits into a grove of
another
• The atlantoaxial joint between the first 2
vertebrae in the neck, which allows the
rotation of the head when saying no is an
example of this.
Ellipsoid Joints
• This joint s also known as a condyloid joint
• This joint allows movement in 2 planes
(flexion, extension; abduction, adduction;
circumduction)
• The wrist is a good example of this
Saddle Joints
• This joint allows for movement in 2 planes
(flexion, extension; abduction, adduction)
but does not allow for rotation.
• An example of this joint is found at the
carpo-metacarpal articulation of the thumb
Ball and Socket Joint
• This joint is also known as a spherodial
joint.
• With this joint, the “ball” at 1 bone fits into
the “socket” of another.
• It allows for movement around 3 axes
(flexion, extension; abduction, adduction;
rotation; circumduction)
• Examples of these joints are hips and
shoulders
Joint Movement
• Uni-axial – joints that allow movement on
1 plane
• Bi-axial – joints that allow movement on 2
planes
• Tri-axial – joints that allow movement on 3
planes
Recap – Type of Joint and
Movement Plane
Joint
Plane
Gliding ---------------------------- uni-axial
Hinge ------------------------------ uni-axial
Pivot ------------------------------- uni-axial
Ellipsoid --------------------------- bi-axial
Saddle ----------------------------- bi-axial
Ball and Socket ------------------ tri-axial
Homework
• Study for quiz on Thursday
• Workbook in chapter 4 fill out definitions
up to ball and socket joint, fill out socket
joint diagram
• For Thursday’s class, quiz on muscular
system, if there is time Ms. Leo will explain
Joint assignment