Joints & Muscles

Classification of Joints

  • Also called articulations

  • Classified by how they can move and how they are joined

  • Fibrous Joints (synarthroses): collagen fibers from one bone penetrate the adjacent bone, anchoring the bones in place.

  • Sutures in the skull are fibrous joints.

  • Cartilaginous Joints (amphiarthroses): joined by cartilage and are slightly movable. 

  • Pubis symphysis and pads between the vertebrae

  • Synovial Joints (diarthroses): freely movable; most numerous and versatile 

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Synovial Joints (Diarthroses)

  • Joint capsule: sheet of connective tissue, goes from periosteum of one bone to the other.

  • Synovial membrane: moist, slippery membrane lines the inside of the joint capsule where it secretes synovial fluid.

  • Joint cavity: small space between bones to allow for movement

  • Synovial fluid: viscous fluid, like an egg white, that lubricates, nourishes the cartilage, and contains phagocytes to remove debris

  • Articular cartilage: thin layer of hyaline cartilage that covers the bones surface, helps prevent friction

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Bursa

  • Small sac filled with synovial fluid called bursa

  • Found in areas where muscles and tendons pass over bony prominences.

  • Knee, shoulder, elbow

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Types of Synovial Joints

  • Six types

  • Ball-and-Socket Joint: widest range of motion

  • Pivot: a projection from one bone articulates with a ring-shaped socket

  • Hinge: only allow back and forth movement

  • Saddle: surfaces of both bones are shaped like a saddle; allows movement back and forth and side to side (limited)

  • Condyloid: oval convex surface on one bone fits into a similarly shaped depression on another; allows flexion and extension and side to side

  • Gliding (plane): two bone surfaces slide over each other; least movable of all the joint

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Movements of Synovial Joints 

  • Flexion: decreases the angle between the joint
  • Extension: increasing the angle between the joint
  • Dorsiflexion: moving the toes or foot upward
  • Plantar Flexion: moving the toes or foot downward
  • Abduction: movement of a body part away from the midline of the body
  • Adduction: movement of a body part toward the midline
  • Circumduction: distal end of an appendage moves in a circle
  • Internal rotation: bone spins toward the body’s midline
  • External rotation: bone spins away from the body’s midline
  • Supination: palm upward
  • Pronation: palm downward
  • Inversion: foot movement that turns sole medially
  • Eversion: foot movement that turns sole laterally
  • Protraction: moves a part forward
  • Retraction: moves a part backward

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Injuries/Diseases

  • Dislocations
  • Ligament tears
  • Joint Replacement (arthroplasty)
  • Arthritis
    • Osteoarthritis: most common
    • Rheumatoid: autoimmune disease

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ROM

  • Active ROM: the patient is able to perform the movements
  • Passive ROM: movement provided by an outside source