Ch 8. Joints
Joints
• Or articulations
• Sites where two bones meet
• 2 fundamental functions
1. Motility
2. Hold skeleton together
- Weakest part of skeleton
Classification of Joints
• Classified by structure and function
• Structural – material binding
– Fibrous
– Cartilaginous
– Synovial joints
• Function – Amount of movement
– Synarthroses – immovable
– Amphiarthroses – slightly movable
– Diarthroses – freely movable
• General –
– fibrous = immobile
– Synovial – freely movable
– Cartilaginous - both
Fibrous Joints
•
•
•
•
•
Bones joined by fibrous tissue
Dense fibrous connective tissue
No joint cavity present
Most are immovable
3 types
1. Sutures
2. Syndesmoses
3. gomphoses
Fibrous Joints
1. Sutures
• “seams”
• Only between bones of skull
• Rigid slices knit bone together
• During middle age – ossifies – closed sutures –
synostoses
• Immobile = protection
(a)
Suture
Joint held together with very short,
interconnecting fibers, and bone edges
interlock. Found only in the skull.
Suture
line
Dense
fibrous
connective
tissue
Figure 8.1a
Fibrous Joints
2. Syndesmoses –
• Bones connected by ligaments
• Only cords or bands of fibrous tissue
• Amount of movement depends on length of
connecting fibers
(b) Syndesmosis
Joint held together by a ligament.
Fibrous tissue can vary in length, but
is longer than in sutures.
Fibula
Tibia
Ligament
Figure 8.1b
Fibrous Joints
3. Gomphoses –
• Peg in socket fibrous joint
• Tooth joint
• Teeth embedded in sockets – periodontal
ligament
(c) Gomphosis
“Peg in socket” fibrous joint. Periodontal
ligament holds tooth in socket.
Socket of
alveolar
process
Root of
tooth
Periodontal
ligament
Figure 8.1c
Cartilaginous Joints
•
•
•
•
Unit articulating bones
Lack joint cavity
Not highly mobile
2 types –
1. Synchondroses
2. Symphyses
Cartilaginous Joints
1. Synchondroses –
• Bones united by bar or plate of hyaline
cartilage
• Epiphyseal plates in long bones of children
• Costal cartilage of first rib
(c) Gomphosis
“Peg in socket” fibrous joint. Periodontal
ligament holds tooth in socket.
Socket of
alveolar
process
Root of
tooth
Periodontal
ligament
Figure 8.1c
Cartilaginous Joints
2. Symphyses –
• “growing together”
• Intervening pad or plate of fibrocartilage
• Compress able and resilience
• Amphiarthrotic joints
• Designed for strength and flexibility
(b)
Symphyses
Bones united by fibrocartilage
Body of vertebra
Fibrocartilaginous
intervertebral
disc
Hyaline cartilage
Pubic symphysis
Figure 8.2b
Synovial Joints
• “joint eggs”
• Articulating bones are separated by a fluid
filled joint cavity
• Freedom of movement
• Freely moveable diarthroses
Synovial Joints General Structure
• 6 distinguishing characteristics:
1. Articular Cartilage – glassy smooth hyaline – articular
cartilage
– Thin, spongy cushions absorb compression
2. Joint (Synovial) Cavity – joint cavity – potential space with a
small amount of synovial fluid
3. Articular Capsule – 2 layered articular capsule or joint
capsule
• Inner synovial membrane – loose CT
4. Synovial Fluid – occupies all free space
• Derived by filtration
• Viscous, egg white consistency
• Slippery weight bearing film – reduces friction
Synovial Joints General Structure
5. Reinforcing Ligaments – band like ligaments
• Usually – capsular or intrinsic ligaments – thickened
parts of fibrous capsule
• Outside capsule – distinct – extra- capsular ligaments
• Deep to it – intracapsular ligaments
6. Nerves and blood vessels – richly supplied with
sensory nerve fibers
• Some detect pain
• Most monitor joint positions and stretch
• Richly supplied with capillary beds – produce filtrate
Synovial Joints General Structure
• Other Components –
– Cushioning fatty pads
– Articular discs – menisci – wedges of fibrocartilage
Ligament
Joint cavity
(contains
synovial fluid)
Articular (hyaline)
cartilage
Fibrous
capsule
Synovial
membrane
Articular
capsule
Periosteum
Figure 8.3
Brusae And Tendon Sheaths
•
•
•
•
Associated with joints
Bags of lubricants
Ball bearings – reduce friction
Bursae – flattened fibrous sacs
– Thin film of synovial fluid
– Occur where ligaments, muscles, skin, tendons, or bones
rub together
• Tendon Sheath –
– Elongated bursae wraps completely around tendon
subjected to friction
– Where several tendons crowded together
Coracoacromial
ligament
Subacromial
bursa
Cavity in
bursa containing
synovial fluid
Humerus
resting
Bursa rolls
and lessens
friction.
Humerus head
rolls medially as
arm abducts.
Humerus
moving
(b) Enlargement of (a), showing how a bursa
eliminates friction where a ligament (or other
structure) would rub against a bone
Figure 8.4b
Stability of Synovial Joints
• Stabilized – so do not dislocate
• Stability depends on –
1. Shape of articular surfaces
2. Number and position of ligaments
3. Muscle tone
Stability of Synovial Joints
1. Articular Surfaces –
• Shapes determine movements possible
• Minor role in stability
• Many joints – shallow sockets – noncomplementary articulating surfaces
• When large – socket deep – stability vastly
improved
Stability of Synovial Joints
2. Ligaments – more ligaments – stronger
• Brace joints
3. Muscle Tone – muscle tendons cross joints
• Tendons taught at all times
• Muscle tone – low levels of contractile activity
in relaxed muscles keep them muscles healthy
and ready to react
Movements Allowed by Synovial Joints
• Muscle origin – attached to immobile or less
movable bone
• Insertion – attached to movable bone
• Muscle contract – insertion moves towards origin
• Nonaxial movement – slipping movements only –
no axis
• Uniaxial movements – movement in 1 plane
• Biaxial movement – movement in 2 planes
• Multiaxial movement – movement in or around
all 3 planes and axes
3 General Types of Movement
1. Gliding
2. Angular Movements
3. Rotations
1. Gliding
•
•
•
•
•
Simplest
One flat bone surface slides over another
Back and forth, side to side
No angulations or rotation
Intercarpal and intercostal joints
Gliding
(a) Gliding movements at the wrist
Figure 8.5a
2. Angular
• Increase or decrease angle between 2 bones
• Any plane of the body
• Include – flexion, extension, hyperextension,
abduction, adduction and circumduction
Hyperextension
Extension
Flexion
(b) Angular movements: flexion, extension, and
hyperextension of the neck
Figure 8.5b
2. Angular
A. Flexion
• Bending movement
• Usually along sagittal plane
• Decrease angle of joint
• Head toward chest
Extension
Hyperextension
Flexion
(c) Angular movements: flexion, extension, and
hyperextension of the vertebral column
Figure 8.5c
2. Angular
B. Extension
• Reverse of flexion
• Occurs at same joints
• Movement along sagittal plane
• Increase the angle
• Straightens a flexed limb or body part
• Ex. Straightening the knee
• Hyperextension – extension beyond anatomical
position
Extension
Hyperextension
Flexion
(c) Angular movements: flexion, extension, and
hyperextension of the vertebral column
Figure 8.5c
2. Angular
C . Abduction
• “moving away”
• Movement of a limb away from the midline
• Along frontal plane
Abduction
Adduction
Circumduction
(e) Angular movements: abduction, adduction, and
circumduction of the upper limb at the shoulder
Figure 8.5e
2. Angular
D. Adduction –
• “moving toward”
• Opposite abduction
• Movement of a limb toward body midline
Abduction
Adduction
Circumduction
(e) Angular movements: abduction, adduction, and
circumduction of the upper limb at the shoulder
Figure 8.5e
2. Angular
E. Circumduction –
• Moving limb so it describes a cone in space
• Distal end of limb moves in a circle
3. Rotation
•
•
•
•
Turning of bone around its long axis
1st – 2 cervical vertebrae
Hip, shoulder
Towards or away from midline
Rotation
Lateral
rotation
Medial
rotation
(f) Rotation of the head, neck, and lower limb
Figure 8.5f
Special Movements
• Do not fit into any of other categories
• Supination “turning backwards” – radius
around ulna
• Pronation – “turning forward” – radius around
ulna
Pronation
(radius
rotates
over ulna)
Supination
(radius and
ulna are
parallel)
(a) Pronation (P) and supination (S)
Figure 8.6a
Special Movements
• Dorsiflexion – increase and decrease
movement of foot, foot superior – approaches
shin
• Plantar Flexion – pointing toes
Dorsiflexion
Dorsiflexion
Plantar
flexion
Plantar
flexion
(b) Dorsiflexion and plantar flexion
Figure 8.6b
Special Movements
• Inversion – sole of foot turns medially
• Eversion – sole face laterally
Inversion
Eversion
(c) Inversion and eversion
Figure 8.6c
Special Movements
• Protraction – anterior movement in
transverse plane
• Retraction – posterior movement in a
transverse plane
Protraction
of mandible
Retraction
of mandible
(d) Protraction and retraction
Figure 8.6d
Special Movements
• Elevation – lift body part superiorly
• Depression – moving elevated part inferiorly
Elevation
of mandible
Depression
of mandible
(e) Elevation and depression
Figure 8.6e
Special Movements
• Opposition – joint between metacarpal 1 and
trapezium
• Movement of thumb
Opposition
(f) Opposition
Figure 8.6f
Types of Synovial Joints
• 6 categories –
1. Plane Joint –
– Flat
– Allow only short non-axial gliding movement
– No rotation
– Non-axial plane joints
f
Nonaxial
Uniaxial
Biaxial
Multiaxial
c
b
a Plane joint (intercarpal joint)
a
e
d
Figure 8.7a
Types of Synovial Joints
2. Hinge Joints –
• Cylindrical end of bone conforms to trough
shaped surface
• Motion – single plane
• Resembles mechanical hinge
• Permit flexion and extension only
f
Nonaxial
Uniaxial
Biaxial
Multiaxial
c
b Hinge joint (elbow joint)
b
a
e
d
Figure 8.7b
Types of Synovial Joints
3. Pivot Joints –
• Rounded end of bone conforms to “sleeve” or
ring composed of bone
• Uniaxial rotation
• Atlas and dens joint
• Ex. Head side to side
f
Nonaxial
Uniaxial
Biaxial
Multiaxial
c
b
c Pivot joint (proximal radioulnar joint)
a
e
d
Figure 8.7c
Types of Synovial Joints
4. Condyloid Joint –
• Also ellipsoidal joint
• Fits into complete depressions in another
articulating surfaces oval
• Angular motion
• Ex. Radiocarpal joints
f
Nonaxial
Uniaxial
Biaxial
Multiaxial
c
b
d Condyloid joint
(metacarpophalangeal joint)
a
e
d
Figure 8.7d
Types of Synovial Joints
5. Saddle Joints –
• Like condyloid joint but allow greater motion
• Both concave and convex areas
• Shaped like a saddle
• Carpometacarpal joint of thumb
f
Nonaxial
Uniaxial
Biaxial
Multiaxial
c
e Saddle joint (carpometacarpal joint
of thumb)
b
a
e
d
Figure 8.7e
Types of Synovial Joints
6. Ball and Sockets –
• Spherical or hemispherical head of one bone
articulates with cup like socket of another
• Multiaxial and most freely moving synovial
• Universal movement – shoulder and hip
f
Nonaxial
Uniaxial
Biaxial
Multiaxial
c
b
f Ball-and-socket joint (shoulder joint)
a
e
d
Figure 8.7f
Synovial Joints- Knee Joint
• Largest, most complex joint of body
• Three joints surrounded by a single joint cavity:
– Femoropatellar joint:
• Plane joint
• Allows gliding motion during knee flexion
– Lateral and medial tibiofemoral joints between
the femoral condyles and the C-shaped lateral and
medial menisci (semilunar cartilages) of the tibia
• Allow flexion, extension, and some rotation
when knee is partly flexed
Femur
Articular
capsule
Posterior
cruciate
ligament
Lateral
meniscus
Anterior
cruciate
ligament
Tibia
Tendon of
quadriceps
femoris
Suprapatellar
bursa
Patella
Subcutaneous
prepatellar bursa
Synovial cavity
Lateral meniscus
Infrapatellar
fat pad
Deep infrapatellar
bursa
Patellar ligament
(a) Sagittal section through the right knee joint
Figure 8.8a
Anterior
Anterior
cruciate
ligament
Articular
cartilage on
lateral tibial
condyle
Articular
cartilage
on medial
tibial
condyle
Lateral
meniscus
Medial
meniscus
Posterior
cruciate
ligament
(b) Superior view of the right tibia in the knee joint, showing
the menisci and cruciate ligaments
Figure 8.8b
Synovial Joints- Knee Joint
• At least 12 associated bursae
• Capsule is reinforced by muscle tendons:
– E.g., quadriceps and semimembranosus
tendons
• Joint capsule is thin and absent anteriorly
• Anteriorly, the quadriceps tendon gives rise
to:
– Lateral and medial patellar retinacula
– Patellar ligament
Quadriceps
femoris muscle
Tendon of
quadriceps
femoris muscle
Patella
Lateral patellar
retinaculum
Medial patellar
retinaculum
Tibial collateral
ligament
Fibular
collateral
ligament
Patellar ligament
Fibula
Tibia
(c) Anterior view of right knee
Figure 8.8c
Synovial Joints- Knee Joint
• Capsular and extracapsular ligaments
– Help prevent hyperextension
• Intracapsular ligaments:
– Anterior and posterior cruciate ligaments
– Prevent anterior-posterior displacement
– Reside outside the synovial cavity
Femur
Tendon of
adductor magnus
Medial head of
gastrocnemius
muscle
Popliteus
muscle (cut)
Articular capsule
Oblique popliteal
ligament
Lateral head of
gastrocnemius
muscle
Bursa
Tibial collateral
ligament
Fibular collateral
ligament
Tendon of
semimembranosus
muscle
Arcuate popliteal
ligament
Tibia
(d) Posterior view of the joint capsule,
including ligaments
Figure 8.8d
Synovial Joint – Shoulder Joint
• Ball-and-socket joint: head of humerus and
glenoid fossa of the scapula
• Stability is sacrificed for greater freedom of
movement
Acromion
of scapula
Coracoacromial
ligament
Subacromial
bursa
Fibrous
articular capsule
Tendon
sheath
Synovial cavity
of the glenoid
cavity containing
synovial fluid
Hyaline
cartilage
Synovial membrane
Fibrous capsule
Tendon of
long head
of biceps
brachii muscle
Humerus
(a) Frontal section through right shoulder joint
PLAY
Animation: Rotatable shoulder
Figure 8.10a
Synovial Joint – Shoulder Joint
• Reinforcing ligaments:
– Coracohumeral ligament—helps support the
weight of the upper limb
– Three glenohumeral ligaments—somewhat weak
anterior reinforcements
Synovial Joint – Shoulder Joint
• Reinforcing muscle tendons:
– Tendon of the long head of biceps:
• Travels through the intertubercular groove
• Secures the humerus to the glenoid cavity
– Four rotator cuff tendons encircle the shoulder
joint:
• Subscapularis
• Supraspinatus
• Infraspinatus
• Teres minor
Acromion
Coracoacromial
ligament
Subacromial
bursa
Coracohumeral
ligament
Coracoid
process
Articular
capsule
reinforced by
glenohumeral
ligaments
Subscapular
Greater
bursa
tubercle
of humerus
Tendon of the
Transverse
subscapularis
humeral
muscle
ligament
Scapula
Tendon sheath
Tendon of long
head of biceps
brachii muscle
(c) Anterior view of right shoulder joint capsule
Figure 8.10c
Acromion
Coracoid process
Articular capsule
Glenoid cavity
Glenoid labrum
Tendon of long head
of biceps brachii muscle
Glenohumeral ligaments
Tendon of the
subscapularis muscle
Scapula
Posterior
Anterior
(d) Lateral view of socket of right shoulder joint,
humerus removed
Figure 8.10d
Synovial Joint – Elbow Joint
• Radius and ulna articulate with the humerus
• Hinge joint formed mainly by trochlear notch
of ulna and trochlea of humerus
• Flexion and extension only
Articular
capsule
Synovial
membrane
Humerus
Synovial cavity
Articular cartilage
Fat pad
Tendon of
triceps
muscle
Bursa
Coronoid process
Tendon of
brachialis muscle
Ulna
Trochlea
Articular cartilage
of the trochlear
notch
(a) Median sagittal section through right elbow (lateral view)
Figure 8.11a
Synovial Joint – Elbow Joint
• Anular ligament—surrounds head of radius
• Two capsular ligaments restrict side-to-side
movement:
– Ulnar collateral ligament
– Radial collateral ligament
Humerus
Anular
ligament
Radius
Lateral
epicondyle
Articular
capsule
Radial
collateral
ligament
Olecranon
process
Ulna
(b) Lateral view of right elbow joint
Figure 8.11b
Articular
capsule
Anular
ligament
Humerus
Coronoid
process
Medial
epicondyle
Ulnar
collateral
ligament
Radius
Ulna
(d) Medial view of right elbow
PLAY
Animation: Rotatable elbow
Figure 8.11d
Synovial Joint - Hip (Coxal) Joint
• Ball-and-socket joint
• Head of the femur articulates with the
acetabulum
• Good range of motion, but limited by the
deep socket
• Acetabular labrum—enhances depth of socket
Coxal (hip) bone
Articular cartilage
Acetabular
labrum
Femur
Ligament of
the head of
the femur
(ligamentum
teres)
Reinforcing ligaments:
Iliofemoral ligament
Pubofemoral ligament
Ischiofemoral ligament
Ligamentum teres
Synovial cavity
Articular capsule
(a) Frontal section through the right hip joint
Figure 8.12a
Synovial Joint - Hip (Coxal) Joint
Reinforcing ligaments:
• Iliofemoral ligament
• Pubofemoral ligament
• Ischiofemoral ligament
• Ligamentum teres
Iliofemoral
ligament
Ischium
Ischiofemoral
ligament
Greater
trochanter
of femur
(c) Posterior view of right hip joint, capsule in place
PLAY
Animation: Rotatable hip
Figure 8.12c
Anterior inferior
iliac spine
Iliofemoral
ligament
Pubofemoral
ligament
Greater
trochanter
(d) Anterior view of right hip joint, capsule in place
Figure 8.12d
Temporomandibular Joint (TMJ)
• Mandibular condyle articulates with the
temporal bone
• Two types of movement
– Hinge—depression and elevation of mandible
– Gliding—e.g. side-to-side (lateral excursion)
grinding of teeth
• Most easily dislocated joint in the body
Mandibular fossa
Articular tubercle
Zygomatic process
Infratemporal fossa
External
acoustic
meatus
Lateral
ligament
Articular
capsule
Ramus of
mandible
(a) Location of the joint in the skull
Figure 8.13a
Mandibular
fossa
Articular disc
Articular
tubercle
Superior
joint
cavity
Articular
capsule
Synovial
membranes
Mandibular
condyle
Ramus of
Inferior joint
mandible
cavity
(b) Enlargement of a sagittal section through the joint
Figure 8.13b
Superior view
Outline of
the mandibular
fossa
Lateral excursion: lateral (side-to-side) movements of the
mandible
Figure 8.13c
Common Joint Injuries
• Sprains
– The ligaments are stretched or torn
– Partial tears slowly repair themselves
– Complete ruptures require prompt surgical repair
• Cartilage tears
– Due to compression and shear stress
– Fragments may cause joint to lock or bind
– Cartilage rarely repairs itself
– Repaired with arthroscopic surgery
Torn
meniscus
Figure 8.14
Common Joint Injuries
• Dislocations (luxations)
– Occur when bones are forced out of alignment
– Accompanied by sprains, inflammation, and joint
immobilization
– Caused by serious falls or playing sports
• Subluxation—partial dislocation of a joint
Homeostatic Imbalances
• Bursitis
– An inflammation of a bursa, usually caused by a
blow or friction
– Treated with rest and ice and, if severe, antiinflammatory drugs
• Tendonitis
– Inflammation of tendon sheaths typically caused
by overuse
– Symptoms and treatment similar to bursitis
Homeostatic Imbalances
• Arthritis –
• >100 different types of inflammatory or
degenerative diseases that damage joints
• Most widespread crippling disease in the U.S.
• Symptoms; pain, stiffness, and swelling of a
joint
• Acute forms: caused by bacteria, treated with
antibiotics
• Chronic forms: osteoarthritis, rheumatoid
arthritis, and gouty arthritis
Homeostatic Imbalances
• Osteoarthritis (OA)
• Common, irreversible, degenerative (“wear-and-tear”)
arthritis
• 85% of all Americans develop OA, more women than
men
• Probably related to the normal aging process
• More cartilage is destroyed than replaced in badly
aligned or overworked joints
• Exposed bone ends thicken, enlarge, form bone spurs,
and restrict movement
• Treatment: moderate activity, mild pain relievers,
capsaicin creams, glucosamine and chondroitin sulfate
Homeostatic Imbalances
• Rheumatoid Arthritis (RA)
• Chronic, inflammatory, autoimmune disease of
unknown cause
• Usually arises between age 40 and 50, but may
occur at any age; affects 3 times as many women
as men
• Signs and symptoms include joint pain and
swelling (usually bilateral), anemia, osteoporosis,
muscle weakness, and cardiovascular problems
Homeostatic Imbalances
• Rheumatoid Arthritis (RA) cont
• RA begins with synovitis of the affected joint
• Inflammatory blood cells migrate to the joint,
release inflammatory chemicals
• Inflamed synovial membrane thickens into a
pannus
• Pannus erodes cartilage, scar tissue forms,
articulating bone ends connect (ankylosis)
Figure 8.15
Homeostatic Imbalances
• Rheumatoid Arthritis (RA) Treatment • Conservative therapy: aspirin, long-term use
of antibiotics, and physical therapy
• Progressive treatment: anti-inflammatory
drugs or immunosuppressants
• New biological response modifier drugs
neutralize inflammatory chemicals
Homeostatic Imbalances
• Gouty Arthritis –
• Deposition of uric acid crystals in joints and
soft tissues, followed by inflammation
• More common in men
• Typically affects the joint at the base of the
great toe
• In untreated gouty arthritis, the bone ends
fuse and immobilize the joint
• Treatment: drugs, plenty of water, avoidance
of alcohol
Homeostatic Imbalances
• Lyme Disease –
• Caused by bacteria transmitted by the bites of
ticks
• Symptoms: skin rash, flu-like symptoms, and
foggy thinking
• May lead to joint pain and arthritis
• Treatment: antibiotics
Developmental Aspects
• By embryonic week 8, synovial joints resemble adult
joints
• A joint’s size, shape, and flexibility are modified by
use
• Advancing years take their toll on joints:
– Ligaments and tendons shorten and weaken
– Intervertebral discs become more likely to
herniate
– Most people in their 70s have some degree of OA
• Exercise that coaxes joints through their full range of
motion is key to postponing joint problems