• Joints
are called articulation
Joint are named or classified according to
o the bones or portion of bones that join together
o the major connective tissue type that binds them together and whether a fluid-filled joint capsule is present
o their degree of motion
degree of motion
cannot be both highly mobile and very strong
• greater the range of motion – weaker the joint
range of motion ?
what is it ?
and different range of motion ?
range of motion = amount of mobility possible for a given joint:
• active range of motion – by muscle contraction
• passive range of motion – movement through outside force acting on joint
• luxation (dislocation) – when articulating surfaces of bones are moved out of proper alignment
luxation
o often damages supporting ligaments and articular cartilage (clinical note p. 206)
o subluxation = partial dislocation
o sprain- when ligaments are damaged – may be stretched or torn
Functional categories ? (table 8.1)
synarthroses, amphiarthroses, diarthroses
common joints in axial skeleton ?
• immovable (synarthroses) and slightly moveable (amphiarthroses) joints more common in axial skeleton
msot common joints in appendicular skeleton ?
• freely moveable (diarthroses) joints more common in appendicular skeleton
Synarthroses
• Synarthroses = immovable joints
o have no joint cavity
o bony edges very close together
o suture – seams between bones
suture ?
sutural ligament = fibrous connective tissue between bones plus continuous periosteum over both surfaces (outer and inner) of connected bones
can be completely immovable in adults
opposing bones interdigitate (interweave) – increases stability
fontanel = found in newborns
• membranous areas between bones
• allows flexibility of skull during birth process and growth of the head after birth
gomphosis
= joint between teeth and alveoli (sockets) of mandible and maxilla
periodontal ligaments = fine bundles of fibrous connective tissue that allow slight give during mastication (chewing)
periodontal disease = plaque and bacteria that migrate from inflamed gingiva (gums) and accumulate in tooth socket
• results in inflammation and destruction of periodontal ligaments leading to tooth loss
• treated by proper brushing, flossing and professional cleaning to remove plaque
synchondrosis
bones joined by hyaline cartilage
sternocostal synchondrosis of first rib
epiphyseal plates of growing bones
• temporary and are converted to synostosis = when epiphysis and diaphysis fuse
amphiarthroses
= slightly moveable joints
o bones farther apart than synarthroses
o syndesmosis (part of amphiarthroses )
ligament made of fibrous connective tissue
distal radius and ulna
o symphysis (part of amphiarthroses )
= wedge or pad of fibrocartilage between bones
manubrium and body of sternum, symphysis pubis, intervertebral disks
• during pregnancy – hormones act on connective tissue of joints – especially symphysis pubis
o become stretchable allowing joints to loosen and pelvic opening to enlarge
• Synovial joints
freely moveable joints
o most complex joints that all contain articular cartilage, a joint capsule, synovial fluid, and accessory structures
o articular cartilage
hyaline cartilage
covers surfaces of articulating bones
o joint capsule
surrounds joint cavity containing synovial fluid
outer fibrous capsule = dense regular connective tissue
• continuous with fibrous layer of periosteum
• portions may thicken forming ligaments
• contains sensory nerve endings – pain and proprioception
inner synovial membrane – lines joint cavity except over articular cartilage
• delicate membrane with mixture of modified connective tissue cells
• produces synovial fluid
o synovial fluid
= serum filtrate and secretions from synovial cells
mixture of polysaccharides, proteins, and lipids
• major polysaccharide = hyaluronic acid
thin layer of fluid lubricates articular surface reducing friction and acts as shock absorber
nourishes chondrocytes
• circulation of synovial fluid by joint movement with cycles of compression and expansion
o accessory structures
pads of cartilage or fat, ligaments, tendons and bursae meniscus (articular disk) fat pads ligaments tendons bursa o bursitis
meniscus
(articular disk) = crescent-shaped pad of fibrocartilage attached to fibrous joint capsule
• allow for variations in shape of articular surface or restricts movements at joint
fat pads
= found around periphery of joint and covered by synovial membrane
• fill spaces and provide protection
ligaments
dense regular connective tissue that support, strengthen and reinforce synovial joints
• intrinsic (intracapsular) ligaments = localized thickening of fibrous layer of joint capsule
• extrinsic (extracapsular) ligaments – separate from and outside of joint capsule
tendons
not part of the articulation but usually pass across or around a joint
bursa
small synovial-filled sacs
• extension of synovial membrane some distance away from joint cavity
• cushion between structures such as tendons on bones and can form tendon sheaths
o bursitis = inflammation of bursa
Classification of synovial joints
• classified based on shape of adjoining articular surfaces which determines range of motion
- gliding (plane ) joint
- pivot joint
- saddle joint
- hinge joint
- ellipsoid joint
- ball and socket joint
gliding (plane ) joint
– provide slight linear motion
monaxial = movement around one axis
pivot joint
– monaxial – restricts movement to rotation around single axis
cylindrical bony process that rotates within ring composed partly of bone and ligament
saddle joint
articular surfaces resemble a saddle – concave on one axis, convex on the other
biaxial = movement around 2 axes situated at right angles to each other
hinge joint
– monaxial joint with convex cylinder in one bone applied to a corresponding concavity in the other
- ellipsoid joint
oval articular surface and corresponding depression in opposing surface
biaxial because shape limits range of motion
- ball and socket joint
head (ball) at end of one bone and cup-shaped socket in adjacent bone
triaxial – allows movement around several axes – wide range of movement
gliding motion
– surfaces slide or glide over one another
angular motion
• based on reference to individual in anatomical position
o one linear structure bends relative to another part of the structure – changing the angle between them
abduction
abduction = movement of appendicular skeleton away from midline (longitudinal axis of the body)
adduction
= movement of appendicular skeleton toward (“adding to”) midline
flexion
= movement in anterior-posterior plane that reduces angle between bones
extension
o = movement in anterior-posterior plane that increases angle between bones
♣ generally straightening from a flexed position
♣ hyperextension = abnormal, forced extension of a joint beyond its normal range of motion
circumduction
= movement in a cone-shape with fixed end proximally located
rotation
rotates a structure around its axis
left or right rotation =
movement of head in “no” position
internal (medial) rotation
= turns long axis of anterior aspect of limb inward
external (lateral) rotation
turns long axis of anterior aspect of limb outward
pronation
rotation of forearm so palm of the hand faces posteriorly
supination
o = rotation of forearm so palm of the hand faces anteriorly (anatomical position)
♣ occurs in freely moveable joints – hip, shoulder
special movements
– unique to only one or two joints
inversion and eversion
turns ankle in, plantar surfaces toward each other or turns out
plantar flexion and dorsiflexion
o = movement of foot - toward floor (standing on toes), or toward shin (walking on heels)
elevation and depression
o movement in superior or inferior direction - mandible open and close, shoulders shrugging
protraction and retraction
o – movement of body part anteriorly or posteriorly – head, mandible, shoulder
♣ lateral and medial excursion – mandible side to side (grinding teeth)
opposition
special movement of thumb that brings pad-to-pad contact with palm or any other finger
fibrocartilage pads
• fibrocartilage pads - separate and cushion symphysis joints between adjacent vertebral bodies from C2 to the sacrum
annulus fibrosus
outer layer of fibrous cartilage surrounded by ring of collagenous fibers
nucleus pulposus
o inner portion
♣ soft, elastic, gelatinous core – 75% water + scattered reticular and elastic fibers
♣ shock absorbers
o movements of vertebral column compress nucleus pulposus and displace it in opposite direction
♣ permits smooth gliding of vertebrae
o accounts for ¼ length of vertebral column
♣ less water content with age and replacement with fibrous cartilage = decrease in height and increase chance of injury (compression fractures)
intervertebral disc disease (IVDD
o painful condition associated with disc degeneration that affects spinal nerves
buliging disc
herniated disc
sciatica
laminectomy
bulging disc
= distortion of annulus fibrosus – partially forcing it into the vertebral canal
herniated disc
♣ rupture of annulus fibrosus with protrusion of nucleus pulposus
• distorts nerves, produces pain, alters function
sciatica
♣ = painful compression of roots of sciatic nerve
• treatment: rest, back braces, analgesics, physical therapy
laminectomy
surgery in 10% of cases -removes disc and vertebral bodies fused together
Shoulder Joint (Fig 8.9)
= glenohumeral joint
• ball and socket joint – loose shallow joint with greatest mobility but least stability
• most commonly dislocated joint in the body – usually dislocated inferiorly into axilla (Clinical note, p.219)
glenoid labrum
fibrocartilage ring that slightly build up the shallow glenoid cavity of the scapula
• stability of joint maintained by glenohumeral ligaments and tendons of four specific appendicular muscles that support shoulder and limit range of motion
rotator cuff
o = four muscles that hold humeral head tightly in glenoid cavity
♣ tendons of supraspinatus, infraspinatus, teres minor, and subscapularis
bursae
• reduce friction where large muscles and tendons pass across the joint capsule
o dense fibrous connective tissue filled with synovial fluid
• common shoulder disorders include: tendinitis, bursitis, and arthritis
Knee Joint
= modified hinge joint between femur and tibia
allows flexion, extension and small amount of rotation
knee joint
structurally composed of 2 joints
• structurally composed of 2 joints:
o tibiofemoral joint – proximal end of tibia and distal end of femur
patellofemoral joint – patella and patellar surface of femur
lateral and medial menisci (knee joint)
= thick articular disks of fibrocartilage deepen the articular surface of the tibia
fat pads (knee)
• around margins of joint aid in cushioning and reducing friction
major tendons and ligaments that provide joint stability (knee)
quadriceps tendons
patellar ligament
o extracapsular ligaments
intracapsular ligaments
quadriceps tendon (knee)
o quadriceps tendon = tendons from muscles responsible for extending lower leg
♣ passes over anterior surface of joint
patella = largest sesamoid bone embedded within tendon
patellar ligament (knee)
extends from patella to tibial tuberosity on anterior surface of tibia
extracapsular ligaments (knee)
♣ tibial (medial) and fibular (lateral) collateral ligaments – stabilize medial and lateral sides respectively
♣ popliteal ligaments – extend on posterior surface from femur to heads of tibia and fibula
intracapsular ligaments – (knee)
o extend between the intercondylar eminence of the tibia to the condyles of the femur
♣ direction names refer to their sites of origin on the tibia
♣ anterior cruciate ligament (ACL) – prevents anterior displacement of tibia relative to femur
• tightens during full extension of knee pushing meniscus between tibia and femur locking knee in place
♣ posterior cruciate ligament (PCL) – prevents posterior displacement of the tibia
number of bursae associated with patella (knee)
o suprapatellar bursa = superior extension of joint capsule that allows the anterior thigh muscles to move over the distal end of the femur
o subcutaneous prepatellar bursitis = ‘housemaid’s knee’ – excessive working on hands and knees
o subcutaneous infrapatellar bursitis = ‘clergyman’s knee’ – excessive kneeling – carpet layers, roofers
• injuries
knee
o blows to the lateral side of the knee far more common than medial side of knee
♣ football tackle to lateral side
o medial meniscus fairly tightly attached to medial collateral ligament and damaged 20 x more than lateral meniscus
♣ torn meniscus – ‘clicking’ sound during extension of leg
♣ anterior cruciate ligament tear – when knee driven anteriorly or hyperextended
• more common in women – from planting foot and twisting
Aging Changes
• tissue repair slows, new blood vessel development decreases, articular cartilage wears down, production of synovial fluid decreases
arthritis
• inflammation of joint leading to pain and stiffness of joint – resulting from infectious agents, metabolic disorders, trauma, immune disorders
o degenerative joint disease (osteoarthritis) = most common type – associated with advanced age – delayed with regular physical activity, stretching and healthy diet
rheumatoid arthritis (RA)
o = second most common type of arthritis
♣ connective tissue disorder
♣ autoimmune disease that predominantly affects joints – commonly destroying small joints in hands and feet
♣ have rheumatoid protein factor in blood