Joints

Joints
Classification of Joints
 Functional classification
(Focuses on amount of movement)
 Synarthroses (immovable joints)
 Amphiarthroses (slightly movable joints)
 Diarthroses (freely movable joints)
 Structural classification
(Based on the material binding them and presence or
absence of a joint cavity)
 Fibrous  mostly synarthroses
 Cartilagenous  mostly amphiarthroses
 Synovial  diarthroses
Table of Joint Types
Functional across
Synarthroses
(immovable joints)
Amphiarthroses
(some movement)
Diarthroses
(freely movable)
Syndesmoses
-ligaments only
between bones; here,
short so some but not
a lot of movement
(example: tib-fib
ligament)
Syndesmoses
-ligament longer
(example: radioulnar
interosseous
membrane)
Structural down
Bony Fusion
Synostosis
(frontal=metopic
suture; epiphyseal
lines)
Fibrous
Suture (skull only)
-fibrous tissue is
continuous with
periosteum
Gomphoses (teeth)
-ligament is
periodontal ligament
Cartilagenous
(bone united by
cartilage only)
Synovial
Synchondroses
-hyaline cartilage
(examples:
manubrium-C1,
epiphyseal plates)
Sympheses
-fibrocartilage
(examples: between
discs, pubic
symphesis
Are all diarthrotic
Fibrous joints
 Bones connected by fibrous tissue: dense
regular connective tissue
 No joint cavity
 Slightly immovable or
not at all
 Types
 Sutures
 Syndesmoses
 Gomphoses
Sutures
 Only between
bones of skull
 Fibrous tissue
continuous with
periosteum
 Ossify and fuse in
middle age: now
technically called
“synostoses”=
bony junctions
Syndesmoses
 In Greek:
“ligament”
 Bones connected
by ligaments only
 Amount of
movement
depends on length
of the fibers: longer
than in sutures
Gomphoses
 Is a “peg-in-socket”
 Only example is
tooth with its
socket
 Ligament is a short
periodontal
ligament
Cartilagenous joints




Articulating bones united by cartilage
Lack a joint cavity
Not highly movable
Two types
 Synchondroses (singular: synchondrosis)
 Sympheses (singular: symphesis)
Synchondroses




Literally: “junction of cartilage”
Hyaline cartilage unites the bones
Immovable (synarthroses)
Examples:
 Epiphyseal plates
 Joint between first rib’s costal cartilage and
manubrium of the sternum
Sympheses
 Literally “growing together”
 Fibrocartilage unites the bones
 Slightly movable (amphiarthroses)
 Resilient shock absorber
 Provide strength and flexibility
 Hyaline cartilage on articular surfaces of bones
to reduce friction
 Examples
 Intervertebral discs
 Pubic symphysis of the pelvis
Synchondroses and sympheses
Also pubic symphsis
Synovial joints
 Include most of the body’s joints
 All are diarthroses (freely movable)
 All contain fluid-filled joint cavity
General Structure of Synovial Joints
1. Articular cartilage



Hyaline
Spongy cushions absorb
compression
Protects ends of bones
from being crushed
2. Joint (synovial) cavity


Potential space
Small amount of synovial
fluid
General structure of synovial joints (cont.)
3. Articular (or joint) capsule

Two layered

Outer*: fibrous capsule of
dense irregular connective
tissue continuous with
periosteum


Inner*: synovial membrane
of loose connective tissue
(makes synovial fluid)
Lines all internal joint
surfaces not covered by
cartilage*
*
*
*
General structure of synovial joints (cont.)
4. Synovial fluid




Filtrate of blood
Contains special glycoproteins
Nourishes cartilage and
functions as slippery lubricant
“Weeping” lubricatioin
5. Reinforcing ligaments (some
joints)



Capsular (most) – thickened
parts of capsule
Extracapsular
Intracapsular
General structure of synovial joints (cont.)
6. Nerves
 Detect pain
 Monitor stretch (one of the
ways of sensing posture
and body movements)
7. Blood vessels
 Rich blood supply
 Extensive capillary beds in
synovial membrane
(produce the blood filtrate)
General structure of synovial joints
Some joints…
 Articular disc or
meniscus
(literally “crescent”)
 Only some joints
 Those with bone
ends of different
shapes or fitting poorly
 Some to allow two kinds of movement (e.g. jaw)
 Of fibrocartilage
 Examples: knee
TMJ (temporomandibular joint)
sternoclavicular joint
Bursae and tendon sheaths




Contain synovial fluid
Not joints but often associated with them
Act like ball bearings
Bursa means “purse” in Latin
 Flattened sac lined by synovial membrane
 Where ligaments, muscles, tendons, or bones
overlie each other and rub together
 Tendon sheath
 Only on tendons subjected to friction
Bursae and tendon sheaths
Joint stability
 Articular surfaces
 Shape usually plays only minor role
 Some deep sockets or grooves do provide stability
 Ligaments
 Usually the more, the stronger the joint
 Can stretch only 6% beyond normal length before
tear
 Once stretched, stay stretched
 Muscle tone
 Constant, low level of contractile force
 Keeps tension on the ligaments
 Especially important at shoulders, knees, arches of
foot
Movements allowed by synovial joints
 Gliding
 Angular movements: hor i the angle between
two bones
DO TOGETHER





Flexion
Extension
Abduction
Adduction
Circumduction
 Rotation
 Special movements
Special movements






Pronation
Supination
Dorsiflexion
Plantar flexion
Inversion
Eversion





Protraction
Retraction
Elevation
Depression
Opposition
Joint movements pics
(from Marieb, 4th ed.)
Synovial joints
classified by shape
(of their articular surfaces)






Plane (see right)
Hinge (see right)
Pivot
Condyloid
Saddle
Ball-and-socket
Selected synovial joints
Shoulder
(glenohumeral) joint
 Stability sacrificed for
mobility
 Ball and socket: head of
humerus with glenoid
cavity of scapula
 Glenoid labrum: rim of
fibrocartilage
 Thin, loose capsule
 Strongest ligament:
coracohumeral
 Muscle tendons help
stability
 Disorders
Rotator cuff muscles add to stability
Biceps tendon is intra-articular
Elbow joint
 Hinge: allows only flexion
and extension
 Annular ligament of
radius attaches to
capsule
 Capsule thickens into:
 Radial collateral
ligament
 Ulnar collateral
ligament
 Muscles cross joint
 Trauma
Wrist joint
Two major joint surfaces
Several ligaments stabilize
1. Radiocarpal joint
 Between radius and
proximal carpals
(scaphoid and lunate)
 Condyloid joint
 Flexion extension
adduction, abduction,
circumduction
2. Intercarpal or
midcarpal joint
 Between the proximal
and distal rows of
carpals
Hip (coxal) joint
 Ball and socket
 Moves in all axes but
limited by ligaments
and deep socket
 Three ext. ligaments
“screw in” head of
femur when standing
 Iliofemoral
 Pubofemoral
 Ischiofemoral
 Acetabular labrum
diameter smaller than
head of femur
 Dislocations rare
 Ligament of head of
femur supplies artery
 Muscle tendons cross
joint
 Hip fractures common
in elderly because of
osteoporosis
Right hip, AP view
Knee joint
 Largest and most complex joint
 Primarily a hinge
 Compound and bicondyloid: femur and
tibia both have 2 condyles
 Femoropatellar joint shares joint cavity
 At least a dozen bursae
 Prepatellar
 Suprapatellar
 Lateral and medial
menisci
 “torn cartilage”
 Capsule absent
anteriorly
 Capsular and
extracapsular ligaments
 Taut when knee
extended to prevent
hyperextension
 Patellar ligament
 Continuation of
quad tendon
 Medial and lateral
retinacula
 Fibular and tibial
collateral ligaments
 Called medial and
lateral
 Extracapsular
 Oblique popliteal
 Arcuate popliteal
Cruciate ligaments
 Cross each other
(cruciate means cross)
 Anterior cruciate (ACL)
 Anterior intercondylar area
of tibia to medial side of
lateral condyl of femur
 Posterior cruciate
 Posterior intercondylar
area of tibia to lateral side
of medial condyl
 Restraining straps
 Lock the knee
Cruciate ligaments
Knee injuries
 Flat tibial surface
predisposes to
horizontal injuries
 Lateral blow: multiple
tears
 ACL injuries
 Stop and twist
 Commoner in women
athletes
 Heal poorly
 Require surgery
Ankle joint
 Hinge joint
 Distal tibia and fibula to talus
 Dorsiflexion and plantar
flexion only
 Medial deltoid ligament
 Lateral ligaments: 3 bands
 Anterior talofibular
 Posterior talofibular
 Calcaneofibular
 Anterior and posterior
tibiofibular (syndesmosis)
Right ankle, lateral view
Temporomandibular
joint (TMJ)
 Head of mandible
articulates with temporal
bone
 Disc protects thin
mandibular fossa of
temporal bone
 Many movements
Demonstrate movements together
 Disorders common
Sternoclavicular joint
 Saddle joint
 Only other example is trapezium
and metacarpal 1 (thumb),
allowing opposion
 Sternum and 1st costal (rib)
cartilage articulate with clavicle
 Very stable: clavicle usually
breaks before dislocation of joint
 Only bony attachment of axial
skeleton to pectoral girdle
Demonstrate movements together
Disorders of joints
 Injuries
 Sprains
 Dislocatios
 Torn cartilage
 Inflammatory and degenerative conditions
 Bursitis
 Tendinitis
 Arthritis
 Osteoarthritis (“DJD” – degenerative joint disease)
 Rheumatoid arthritis (one of many “autoimmune” arthritites)
 Gout (crystal arthropathy)