Articulations or Joints

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Articulations or Joints

• Articulation or Joint
• Place where two bones (or bone and cartilage)
  come together
• Arthrology study of the joints
• Kinesiology study of musculoskeletal
• Functions of joints
• Give the skeleton mobility
• Hold the skeleton together
• Structure correlated with movement

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Classification of Joints

• Structural classes based on type of connective
  tissue type that binds bones and whether or not a
  joint cavity is present
• Fibrous
• Cartilaginous
• Synovial
• Functional classes based on degree of motion
• Synarthrosis non-movable
• Amphiarthrosis slightly movable
• Diarthrosis freely movable

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Fibrous Joints

• Characteristics
• United by fibrous connective tissue
• Have no joint cavity
• Move little or none
• Types
• Sutures
• Syndesmoses
• Gomphoses

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Fibrous Joints Sutures

• Types of sutures
• Serrated Opposing bones interdigitate (Sagittal
  suture)
• Lap Overlapping beveled edges (Squamosal suture)
• Plane Straight, non-overlapping edges
  (Intermaxillary suture)
• Periosteum of one bone is continuous with the
  periosteum of the other.
• In adults may ossify completely synostosis.
• Fontanels membranous areas in the suture between
  bones. Allow change in shape of head during birth
  and rapid growth of the brain after birth.

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Types of Sutures
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Fibrous Joints Syndesmoses

• Two bones joined by ligament
• Interosseous membrane
• Most moveable of fibrous joints
• Examples radioulnar joint and tibiofibular joints

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Fibrous Joints Gomphoses

• Specialized joints
• Pegs that fit into sockets
• Periodontal ligaments hold teeth in place
• Inflammations
• Gingivitis leads to
• Periodontal disease

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Cartilaginous Joints

• Bones are joined by cartilage
• Lack a joint cavity
• Types
• Synchondroses bound by hyaline cartilage
• Symphyses bound by fibrocartilage

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Cartilaginous Joints Synchondroses

• Joined by hyaline cartilage
• Little or no movement
• Some are temporary and are replaced by synostoses
• Some are permanent
• Some like costochondral joints develop into
  synovial joints
• Examples Epiphyseal plates, 1st sternocostal

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Cartilaginous Joints Symphyses

• Fibrocartilage uniting two bones
• Slightly movable
• Examples symphysis pubis, between the manubrium
  and the body of the sternum, intervertebral
  disks.

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Synovial Joints

• Contain synovial fluid in a joint cavity called
  the synovial cavity
• Allow considerable movement (diarthroses)
• Most joints that unite bones of appendicular
  skeleton reflecting greater mobility of
  appendicular skeleton compared to axial

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Structure of Synovial Joints

• Articular cartilage
• Hyaline cartilage that covers epiphysis
• Absorbs compression of joint
• Joint cavity (synovial cavity)
• Unique to synovial joints
• Cavity is a potential space that holds small
  amount of fluid
• Articular Capsule - a 2 layered capsule
• Fibrous capsule - Dense irregular c.t.
• Strengthens joint
• Synovial membrane - Loose c.t.
• Lines joint capsule and covers internal joint
  surfaces
• Functions to make synovial fluid
• Synovial fluid
• Viscous fluid similar to raw egg white
• A filtrate of blood from capillaries in synovial
  membrane
• Contains glycoprotein molecules secre-ted by
  fibroblasts
• Nerves in capsule help brain know position of
  joints (proprioception)

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Synovial Joints with Articular Discs

• Some synovial joints contain an articular disc
• Occur in the temporomandibular joint and at the
  knee joint
• Occur in joints whose articulating bones have
  somewhat different shapes

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Bursae and Tendon Sheaths

• Bursae and tendon sheaths are not synovial joints
• Closed bags of lubricant
• Reduce friction between body elements
• Bursa a flattened fibrous sac lined by a
  synovial membrane
• Tendon sheath an elongated bursa that wraps
  around a tendon

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Synovial Joints Friction-Reducing Structures
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Factors Influencing Joint Stabililty

• Articular surfaces seldom play a major role in
  joint stability
• The elbow, the knee and the hip do provide
  stability
• Ligaments the more ligaments in a joint, the
  stronger it is
• Muscle tone the most important factor in joint
  stability
• Keeps tension on muscle tendons

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Types of Movement

• Gliding in plane joints slight movement
• Angular
• Flexion and Extension
• Hyperextension
• Plantar and Dorsiflexion
• Abduction and Adduction
• Circular
• Rotation
• Pronation and Supination
• Circumduction

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Flexion and Extension

• Flexion movement of a body part anterior or
  posterior to the coronal plane
• Extension movement of a body part posterior or
  anterior to the coronal plane
• Dorsoflexion - foot lifted toward the shin
• Plantar flexion - pointing toes downward
• Abduction movement away from the midline
• Adduction movement toward the midline

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Circular Movements Rotation, Pronation and
Supination

• Rotation turning of a structure on its long axis
• Examples rotation of the head, humerus, entire
  body
• Medial and lateral rotation example, the
  rotation of the arm
• Pronation/Supination refer to unique rotation of
  the forearm
• Pronation palm faces posteriorly
• Supination palm faces anteriorly
• Circumduction

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Special Movements

• Unique to only one or two joints
• Types
• Elevation and Depression
• Protraction and Retraction
• Opposition and Reposition
• Inversion and Eversion

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Movements at Synovial joints

• Monoaxial occurring around one axis
• Biaxial occurring around two axes at right
  angles to each other
• Multiaxial occurring around several axes

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Types of Synovial JointsPlane Joints

• Plane or gliding joints
• Monaxial. One flat bone surface glides or slips
  over another similar surface
• Sometimes considered an amphiarthrosis
• Examples intervertebral, intercarpal,
  intertarsal acromioclavicular, carpometacarpal,
  tarsometatarsal,

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Hinge and Pivot Joints

• Hinge joints
• Monaxial
• Convex cylinder in one bone corresponding
  concavity in the other
• Example elbow, ankle, interphalangeal
• Pivot joints
• Monaxial. Rotation around a single axis.
• Cylindrical bony process rotating within a circle
  of bone and ligament
• Example articulation between dens of axis and
  atlas (atlantoaxial), proximal radioulnar

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Types of Synovial Joints

• Saddle joints
• Each articular surface is shaped like a saddle
• Trapeziometacarpal joint at base of the thumb
  

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Ball-and-Socket and Ellipsoid Joints

• Ball-and-socket
• Smooth heispherical head fits within a cuplike
  depression
• Multiaxial
• Examples shoulder and hip joints
• Condyloid (ellipsoid) joint
• Oval convex surface on one bone fits into a
  similarly shaped depression on the next
• Atlantooccipital joint (C1-C2)
• Metacarpophalangeal joints

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The Knee Joint

• Most complex diarthrosis
• patellofemoral gliding joint
• tibiofemoral gliding with slight rotation and
  gliding possible in flexed position
• Joint capsule anteriorly consists of patella and
  extensions of quadriceps femoris tendon
• Capsule strengthened by extracapsular and
  intracapsular ligaments

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Knee, cont.

• Cruciate ligaments extend between intercondylar
  eminence of tibia and fossa of the femur
• Anterior cruciate ligament (ACL). Prevents
  anterior displacement of tibia
• Posterior cruciate ligament (PCL). Prevents
  posterior displacement of tibia
• Collateral and popliteal ligaments along with
  tendons of thigh muscles strengthen the joint
• Bursae may result in slow accumulation of fluid
  in the joint (water on the knee)

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Knee Joint Anterior and Posterior Views

• Anterior and lateral cruciate ligaments limit
  anterior and posterior sliding movements
• Medial and lateral collateral ligaments prevent
  rotation of extended knee

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Knee Joint Superior View

• Medial and lateral meniscus absorb shock and
  shape joint

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Knee Injuries and Disorders

• Football injuries often tear the tibial
  collateral ligament, the anterior cruciate
  ligament, and damage the medial meniscus
• Bursitis

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Inflammatory and Degenerative Conditions

• Arthritis describes over 100 kinds of
  joint-damaging diseases
• Osteoarthritis most common type wear and
  tear arthritis
• Rheumatoid arthritis a chronic inflammatory
  disorder
• Gouty arthritis (gout) uric acid build-up
  causes pain in joints
• Lyme disease inflammatory disease often
  resulting in joint pain

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Effects of Aging on Joints

• Tissue repair slows rate of new blood vessel
  development decreases
• Articular cartilages wear down and matrix becomes
  more rigid
• Production of synovial fluid declines
• Ligaments and tendons become shorter and less
  flexible decrease in range of motion (ROM)
• Muscles around joints weaken
• A decrease in activity causes less flexibility
  and decreased ROM