SKELETAL FRICTION
Joints
Chapter 8
Objectives
• Name the three major structural types of joints and
compare their structure and mobility.
• Identify to which of these three structural types any
joints in the body belong.
• Classify synovial joints according to movement
permitted. –
• Outline the structure and functions of bursae and
tendon sheaths.
INTRODUCTION & OBJECTIVES
Classified by:
Structure - fibrous, cartilaginous, synovial
Function - synarthroses, amphiarthroses, diarthroses
Joints perform two functions
in the body:
1. they hold the skeletal
bones together
2. they allow the rigid
skeleton some flexibility
so that gross movements
can occur.
Functionally joints are classified as:
1. immovable joints (= synarthroses: arthrose=joint,
syn=together - bone stuck together),
2. slightly movable joints (= amphiarthroses: arthrose=joint,
amphi=both - in between immovable and freely movable ),
3. freely movable joints (= diarthroses: arthrose=joint,
dia=apart - bone apart, can move easily).
Their structural classification is based on the
nature of the material comprising them.
Structurally joints are classified as
1. fibrous joints (joints held together by fibrous connective
tissue and with no joint cavity),
2. cartilaginous joints (held together by cartilage, lacking a
joint cavity)
3. synovial joints (in which the joint contains a synovial
cavity).
FIBROUS JOINTS
(Synarthroses or Immovable)
1. Syndesmoses- ligaments
connect bones; slightly
mobile Ex. radioulnar
articulation
2. Sutures- interlocking
junctions with fibrous
tissue Ex. Skull
3. Gomphoses- roots of teeth
and alveolar processes,
called periodontal
membrane and ligament
Ex. teeth and mandible
• In fibrous joints the bones are united by dense
connective tissue consisting of collagen fibers which run
between the bones. There is NO JOINT CAVITY. The
degree of movement permitted depends on the length of
the collagen fibers, and on the shape and extent of the bone
surface at the joint: most of the fibrous joints are
immovable - a few are slightly movable.
CARTILAGINOUS JOINTS:
In cartilaginous joints the bones are united with each other
by cartilage. Again, there is NO JOINT CAVITY.
Amphiarthroses or Slightly
Movable
1. Synchondroses- use hyaline
cartilage
Ex. costal cartilage;
epiphyseal plate
2. Symphyses- use
fibrocartilage
Ex. symphysis pubis;
intervertebral disks
SYNOVIAL JOINTS: Joint cavity.
Diarthroses or Freely Movable
A. Structure 
1. Synovial Membrane- secretes synovial fluid
(lubrication)
2. Joint cavity- contains synovial fluid aka bursa
3.Articular Cartilage- hyaline; absorb compression
4. Reinforcing ligaments
Synovial joints are reinforced by a number of
ligaments. Ligaments are bands of dense regular
connective tissue proper that connect bones to
other bones. (Please do NOT mistake them for
TENDONS: bands of dense regular connective
tissue proper that connect muscles to bones.) The
ligaments may be part of the fibrous capsule
(intrinsic or capsular ligaments), or may be distinct
from the fibrous capsule and found outside the
capsule (extracapsular ligaments)or deep to it
(intracapsular ligaments). Since intracapsular
ligaments are covered with synovial membrane they
do not actually lie within the joint cavity.
In some joints such as the knee, complete or
partial discs (menisci) of fibrocartilage occur
within the synovial cavity. They do not function
in weight bearing, but act as swabs to spread
synovial fluid into the joint, and help to stabilize
the joint. These discs (often called `knee
cartilages') are frequently torn or displaced in body
contact sports .
The majority of articulations between
bones are synovial joints.
All synovial joints are freely
moveable joints.
They are characterized by
the PRESENCE OF A
closed space or CAVITY
between the bones: the joint
cavity ( synovial cavity).
Bursae
• Bursae (singular = bursa) are
closed, partially collapsed balloon
containing synovial fluid and
lined with synovial membrane on
the inside and a fibrous membrane
on the outside. They are found in
the vicinity of joints where
movement between two adjacent
tissues might otherwise result in
excessive friction. They are
located between any two of bone,
tendon, muscle or skin and they
prevent these organs to rub against
each other: like the joint cavity,
with which they frequently
connect, they serve to reduce
friction.
SYNOVIAL JOINTS:
Tendon sheath.
• Tendon sheaths are
similar to bursae, but
differ in shape. They look
like sausage-shaped
balloons that wrap around
long tendons subjected to
friction.
Three factors determine the strength or
stability of the synovial joint, and the range of
movement permitted by it. These are:
1. The shape of the articular surfaces of the
bones
2. The ligaments: strong bands of dense fibrous
connective tissue which bind the adjacent bones
together,
3. Muscles which extend between the two bones
comprising the joint.
Synovial Joint Movement Options
• Use goniometer to measure angles and range of
motion of joints after injury; information aids in
designing rehabilitation plans
Gliding Movements:
simplest joint
movement; no
angular or circular
mov’t; sliding
Angular Movements
1. Flexion- decrease angle;
bending; folding;
withdrawing a part
2. Extension &
Hyperextension- increasing
angle; stretching too far
3. Plantar Flexion &
Dorsiflexion- foot down and
back/ flex foot up
4. Abduction & Adductionmove away from median/
move towards median of
body
Rotation Movements
• pivot bone around
its own long axis;
make a circle;
medial & lateral
Special
Movements
• Supination &
Pronation- turn
hand palm side up
“soup”/ palm side
down “pro BBALL”
• Inversion &
Eversion- sole of
foot medial/ sole of
foot lateral
Special Movements
• Protraction &
Retraction- part
forwards/ part
backwards
• Elevation and
Depression- part up/
part down
• Opposition – touch
thumb to other
fingers; fine motor
skills
Synovial joints are classified according to
the shape of the articulating surfaces
which, in turn, determines the range of
movement permitted. They can be
classified into six major categories:
1. Glding Ex. Wrists, vertebrae
2. Hinge- flexion & extension
Ex. Elbow
3. Pivot- rotation
1. Ex. dens of axis for skull to rotate “no”
4. Saddle-Ex. thumb fits into saddle-shaped trapezium bone
5. Bll & Socket- MOST RANGE OF MOTION; Ex. head of femur
and acetabulum of coxal bone
SYNOVIAL JOINTS:
Plane (gliding)
• Opposite bone surfaces are
flat or slightly curved.
• Only sliding motion in all
directions are allowed.
Since there is no bone
movement around an axis,
the joints are nonaxial.
SYNOVIAL JOINTS:
Hinge
• Convex surface of one bone
fits smoothly into concave
surface of the second bone
• The movements allowed are
similar to those allowed by a
mechanical door hinge.
Since the movements
(flexion/extension) are all in
one plane and around one
axis, the joints are uniaxial
SYNOVIAL JOINTS:
Pivot
• A rounded, pointed or
conical surface of one
bone is inserted into a ring
made partly of another
bone and partly of a
ligament.
• Since the only movement
allowed is the rotation of
one bone around its own
axis, the Joints are
uniaxial
SYNOVIAL JOINTS:
Saddle
• First bone's articular surface
is concave in one direction
and convex in the other
while the second bone is just
the opposite (or if you
prefer, one bone is shaped
like a saddle, and the other
is shaped like its rider
SYNOVIAL JOINTS:
Saddle
• The saddle joint is similar to the
Ellipsoidal Joint but the
movements are freer. The
movements allowed are
flexion/extension,
adduction/abduction and
circumduction but NO
ROTATION. Since bones can
move in both planes: side to side
and back and forth movements
the joints are biaxial.
SYNOVIAL JOINTS:
Ball and Socket.
• Ball-shaped head fits into a
cup-shaped depression
• These joints are the most
freely moving of all synovial
joints. The movements are
allowed in all axes and
planes: flexion/extension,
adduction/abduction,
circumduction and rotation.
These joints are multiaxial