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Chapter 9
Joints
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Joints (articulations or arthrosis) hold bones together but
permit movement
Point of contact
 between two bones
 between cartilage and bone
 between teeth and bones
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Arthrology study of joints
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Kinesiology  study of motion
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Structural classification is based on the presence
or absence of a synovial (joint) cavity and type of
connecting tissue. Structurally, joints are
classified as
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fibrous, cartilaginous, or synovial.
Functional classification based upon movement:
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immovable  synarthrosis
slightly movable  amphiarthrosis
freely movable  diarthrosis
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Lack a synovial cavity
Bones held closely
together by fibrous
connective tissue
Little or no movement
(synarthroses or
amphiarthroses)
Three structural types
sutures
 syndesmoses
 gomphoses

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Thin layer of dense
fibrous connective tissue
unites bones of the skull
Immovable (synarthrosis)
If fuse completely in
adults is synostosis
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Fibrous joint
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bones united by
ligament
Slightly movable
(amphiarthrosis)
Anterior
tibiofibular joint
and Interosseous
membrane
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Ligament holds cone-shaped peg in bony socket
Immovable (amphiarthrosis)
Teeth in alveolar processes
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Lacks a synovial cavity
Allows little or no movement
Bones tightly connected by fibrocartilage or
hyaline cartilage
Two types
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synchondroses
symphyses
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Connecting
material is hyaline
cartilage
Immovable
(synarthrosis)
Epiphyseal plate
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Fibrocartilage is
connecting
material
Slightly movable
(amphiarthroses)
Intervertebral
discs and pubic
symphysis
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The articular capsule surrounds a diarthrosis, encloses
the synovial cavity, and unites the articulating bones.
The articular capsule is composed of two layers - the
outer fibrous capsule (which may contain ligaments) and
the inner synovial membrane (which secretes a
lubricating and joint-nourishing synovial fluid).
The flexibility of the fibrous capsule permits
considerable movement at a joint, whereas its great
tensile strength helps prevent bones from dislocating.
Other capsule features include ligaments and articular
fat pads.
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
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Synovial cavity
separates
articulating bones
Freely moveable
(diarthroses)
Articular cartilage

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Articular capsule

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reduces friction
absorbs shock
surrounds joint
thickenings in
fibrous
capsule called
ligaments
Synovial membrane

inner lining of
capsule
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
Synovial Membrane

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secretes synovial fluid
containing slippery hyaluronic acid
brings nutrients to articular cartilage
Accessory ligaments

extracapsular ligaments
 outside joint capsule

intracapsular ligaments
 within capsule
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Articular discs or menisci
attached around edges to capsule
 allow two bones of different shapes to fit tightly
 increase stability of knee - torn cartilage

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Bursae saclike structures between structures

skin/bone or tendon/bone or ligament/bone
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Nerves to joints are branches of nerves to
nearby muscles
Joint capsule and ligaments contain pain
fibers and sensory receptors
Blood supply to the structures of a joint are
branches from nearby structures

supply nutrients to all joint tissues except the
articular cartilage which is supplied from the
synovial fluid
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Bursae
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fluid-filled saclike extensions of the joint capsule
reduce friction between moving structures
 skin rubs over bone
 tendon rubs over bone
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Tendon sheaths

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tubelike bursae that wrap around tendons at wrist
and ankle where many tendons come together in a
confined space
Bursitis

chronic inflammation of a bursa
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Bone surfaces are flat or slightly
curved
Side to side movement only
nonaxial
Rotation prevented by ligaments
Examples
 intercarpal or intertarsal joints
 sternoclavicular joint
 vertebrocostal joints
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Convex surface of one bones fits into
concave surface of another bone
Uniaxial like a door hinge
Examples
 Knee, elbow, ankle, interphalangeal
joints
Movements produced
 flexion = decreasing the joint angle
 extension = increasing the angle
 hyperextension = opening the joint
beyond the anatomical position
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Rounded surface of bone
articulates with ring formed by
another bone and ligament
Monoaxial since it allows only
rotation around longitudinal axis
Examples
 Proximal radioulnar joint
 supination
 pronation
 Atlanto-axial joint
 turning head side to side
“no”
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Oval-shaped projection fits into oval (elliptical) depression
Biaxial  flex/extend or abduct/adduct and circumduction are possible
Examples
 wrist and metacarpophalangeal joints for digits 2 to 5
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One bone saddled-shaped; other bone fits as a person would sitting in that saddle
Biaxial
Movements are flexion-extension, abduction-adduction, and circumduction
 Circumduction allows tip of thumb travel in circle
 Opposition allows tip of thumb to touch tip of other fingers
Example
 trapezium of carpus and metacarpal of the thumb
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Ball fitting into a cuplike
depression
Multiaxial
 flexion/extension
 abduction/adduction
 rotation/circumduction
Examples (only two)
 shoulder joint
 hip joint
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Structure and shape of the articulating bone
Strength and tautness of the joint ligaments
Arrangement and tension of the muscles
Contact of soft parts
Hormones
Disuse
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Head of humerus and
glenoid cavity of scapula
Ball and socket
Articular capsule from
glenoid cavity to
anatomical neck
Glenoid labrum deepens
socket
Many nearby bursa
(subacromial)
Associated ligaments
strengthen joint capsule
Transverse humeral
ligament holds biceps
tendon in place
All types of movement
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Attach humerus to scapula
Encircle the joint supporting the capsule
Hold head of humerus in socket
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Strength/Stability of joint-deep shoulder muscles/tendons
Deep shoulder muscles:
Subscapularis
nearly
Supraspinatus
complete
Infraspinatus
 circle 
Teres minor
around
joint
Musculotendinus
(rotator) cuff
frequent site of
injury- pitchers/
quarterbacks
“tearing” supraspinatus muscle
Shoulder separation- dislocation of acromioclavicular
joint or
displacement of humerus from
glenoid cavity
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This ball-and-socket joint is
formed by the head of the femur
and the acetabulum of the
hipbone.
This is an extremely stable joint
due to the bones making up the
joint and the accessory ligaments
and muscles.
Movements at this joint include
flexion, extension, abduction,
adduction, circumduction, and
medial and lateral rotation of the
thigh.
One of strongest structures in the
body
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This is the largest and most
complex joint of the body and
consists of three joints within a
single synovial cavity.
Between femur, tibia and
patella
Hinge joint between tibia and
femur
Gliding joint between patella
and femur
Flexion, extension, and slight
rotation of tibia on femur when
knee is flexed
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
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Articular capsule
Patella is part of joint
capsule anteriorly
Rest of articular capsule is
extracapsular ligaments
 Fibular and tibial
collateral ligaments
Posterior cruciate
ligament
Anterior cruciate ligament
 Lateral and medial
menisci = articular
discs
Many bursa
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Knee Injuries
and Disorders
•Knee injuries-sports
•3c’s
• rupture of tibial collateral ligament;
•tear of anterior cruciate ligament
•torn cartilage( medial meniscus)
•Usually- difficult repair/recovery
•Dislocated knee•displacement of tibia relative to
femur
•Anterior (most common)/ posterior/
medial/lateral
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DISORDERS: HOMEOSTATIC IMBALANCES
Joint Disorders
Rheumatismany painful state of supporting
structures of the body(bones, ligaments, joints, tendons or muscles)
Arthritusrheumatism of joints
Rheumatoid arthritis (RA)
autoimmune disease- body attacks its own tissue
Immune system attacks cartilage/joint linings
Bilateral- joint on one side/opposite side
Inflammation of synovial membrane
untreated-membrane thickens-synovial fluid accumulates
pressure- pain /tenderness
Pannus- abnormal granulation-produced by membrane;
erosion of articular cartilage; cartlilage destroyed;
fibrous tissue joins bone ends;
tissue ossifies-fusion of joint (immoveable)
Treatmentnot specific- reduce pain/inflammation;
preserve muscle strength/ joint function
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DISORDERS: HOMEOSTATIC IMBALANCES
Osteoarthritus ( more common than RA; less damaging)
deterioration of articular cartilage;
new bone formation in joint (“spurs”/bumps)
decrease joint movement)
Treatment-surgery-remove spurs
Gouty arthritis (genetic disorder-males)
Uric acid-waste product of nucleic acid metaboloism
 uric acid/unable to excrete;
uric acid sodium urate (crystals) deposited in soft tissues/joints

inflammation/swelling
Treatment- diet/colchicine uric acid production
Bursitis- acute chronic inflammation of a bursa
housemaid’s knee/ carpet layers knee
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DISORDERS: HOMEOSTATIC IMBALANCES
Dislocation (luxation)displacement of a bone from a joint;
tearing of ligaments, tendons and articular capsules
Partial dislocation (subluxation)incomplete displacement of bone from a joint
Sprainforced wretching/twitching of a joint with possible rupture or injury
to its attachments without dislocation (luxation)
possible damage-blood vessels/muscles/tendons/ligaments/or nerves
Strain (less serious)overstretching of a muscle
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