Download Joints

Joints
Dr. Anderson
GCIT
Joints
• Where two or more
bones meet
• Function
– Connection (ligaments)
– Movement (muscles)
– Protection (joint
capsule)
Joint Classification
Structural
Functional
Fibrous – synostoses
(immovable), syndesmoses
(variable movement),
gomphoses (peg-in-socket)
Cartilaginous –
synchondroses, symphyses
Synarthroses – bones
don’t move relative to
each other
Synovial – articulating
bones are separated by a
fluid-filled cavity (most
joints)
Diarthroses – freely
moveable
Amphiarthroses –
“slightly” moveable
Sutures
• Fibrous joints, slightly
mobile in youth,
immobile as adult (e.g.
cranial sutures)
– Limited mobility allows
brain to grow during
development
– Immovability as adult
serves as a protective
function
Top of Skull (newborn baby)
Syndesmoses
• Bones connected
exclusively by ligaments
• Movement varies
according to length of
the ligaments forming
the joint, e.g.:
– Very limited movement
between tibia and fibula
– Very pronounced
movement of ulna
around radius
Gomphoses
• Peg-in-socket, fibrous joint
• Only example is the teeth in their alveolar cavities
connected by the periodontal ligament
Cartilaginous Joints
• Articulating bones are united by cartilage
– Synchondroses and symphyses
Synchondroses
• Cartilage that unites
two bones (such as
the epiphyses to the
diaphyses in the long
bones of children and
young adults)
• E.g. Epiphyseal plates
Symphyses
• Where articulating
bones are lined with
cartilage, which is fused
to a pad or plate of
fibrocartilage
– E.g. – intervertebral
discs, pubic symphysis
Synovial Joints
• Features
1. Articular cartilage – covers opposing bone surface
2. Synovial cavity – space that contains synovial fluid
3. Articular Capsule – provides tensile strength and
covers all surfaces not lined with cartilage
4. Synovial fluid – provides joint lubrication,
released from the cartilage itself during activity
(weeping lubrication)
5. Reinforcing ligaments
6. Nerves and blood vessels innervate and perfuse,
respectively
Joint Structure
What holds joints together?
• Articular Surfaces -Deeply fitting articulations
more stable than shallow ones
• Ligaments – “cables” of dense regular
connective tissue that hold the joint together
– Relatively little stretch (can snap)
• Muscle Tone – low levels of contractile activity
– more tone = more stable joints
Synovial Joint Structure
Articular Capsule
• Continuous with
periosteum
• Effectively “seals”
joint, keeping the
synovial fluid
(lubricating fluid)
around the articular
surfaces
Articular Discs (Menisci)
• Fibrocartilage pads
that partially or
completely divide
the synovial cavity
– (Knee, jaw meniscus)
• Improve the fit of
some articular
surfaces in the joint
Bursae and Tendon Sheaths
• Fibrous connective
tissue that serves as a
pliable “ball bearing”
for some joints (e.g.
shoulder) and closely
packed tendons (e.g.
wrist)
• Bursa rolls in opposing
direction of movement
Carpal Tunnel Syndrome
• Repetitive motion
can inflame tendon
sheaths in the wrist
(the carpal tunnel)
pressing on nerves
and causing pain
Joint Movements
• Originates from muscle contraction (of course)
• Degree of joint movement is called “range of
motion”
• Three main types
– Gliding
– Angular
– Rotation
Angular Movement
• Flexion – pulling the joint angle closed
• Extension – opening the joint angle
– Hyperextension – greater than normal extension
• Abduction – moving a limb away from the median line of
the body
• Adduction – moving a limb toward the median line of
the body
• Circumduction – moving a limb in a cone-shaped path in
space
Rotation
• Turning of a bone
around its long axis
– Medial rotation –
turning toward the
midline
– Lateral rotation –
turning away from
the midline
Supination and Pronation
• Refer to movement of radius around the ulna
• With arms down at sides:
– Supination is a lateral rotation of the palms (palms
anterior or up)
– Pronation is a medial rotation of the palms (palms
face posteriorly, radius and ulna cross each other,
forming an ‘X’)
Ankle and Foot Movement
• Dorsi flexion – moves
foot up (superiorly)
• Plantar flexion – moves
foot down (inferiorly)
• Inversion – sole of foot
turns medially
• Eversion – sole turns
laterally
Synovial Joint Types
• Plane (Gliding) – allow only short, gliding movements
(wrist and ankle)
• Hinge (One angular direction) - allows motion only
along a single plane (flexion and extension only)
• Pivot (Rotation) – allows the bone to rotate around its
axis
• Condyloid (All angular directions)– Oval articulating
surfaces that permit movement in all directions
• Saddle (All angular directions)– both articular surfaces
have a convex AND a concave side that articulate
together
• Ball-and-Socket - (Universal movement) allows
movement in all directions, including limited rotation
Gliding joints
• Simplest movement
– One or more flat
(usually) bone
surfaces glide over
another
• Wrist bones
• Ankle bones
• Between vertebrae
Knee Joint
• Very Complex
– 4 bones
• Femur, tibia, fibula,
patella
– Ligaments often
injured in sports or
accidents
Knee Injuries
• Cruciate Ligaments
– ACL (anterior)
– PCL (posterior)
• Deep in joint cavity of
knee (intracapsular)
– Can tear and separate
femur from the tibia
– Most often happens
when the knee is
rotated during full
extension
Torn ACL (Arthroscopic view)
Knee Injuries
• Most dangerous
injuries are lateral
blows to the fully
extended knee
– Torn menicsi
– Torn collateral
ligaments
• Tibial (Medial or
MCL)– outside hit
• Fibular (Lateral or
LCL)– inside hit
Jaw movements
• Protraction and
retraction – jutting
jaw out and bringing
it back, respectively
• Elevation and
Depression – Moving
a body part superiorly
or inferiorly (e.g. jaw)
Jaw Joint Problems
• Jaw Joint (mandible
and mandibular fossa)
is called the temperomandibular joint (TMJ)
• Loosely connected –
has a greater range of
motion than other
hinge joints
– Condyle of mandible
can move out of the
fossa, (anterior
disarticulation)