Joints

Articulations information

• points where bones come together, joints

• arthr- = joint

• arthritis= inflammation of the joints

• classified by structure or function

Structural Classification of Joints

• Fibrous- joint with no joint cavity

  • bones held together by fibrous connective tissue

  • sutures between bones of the skull are fibrous joints

• Cartilagenous= lacks a joint cavity

  • bones held together by cartilage

  • pubic symphysis

• Synovial- fluid filled cavity (synovial cavity)

  • bones held together by synovial capsule and often there are accessory ligaments

Functional classification of joints

• synarthroses- joints that allow virtually no movement

  • sutures

• amphiarthroses- joints that allow limited movement

  • pubic symphysis

• Diarthroses- joints that allow free movement

  • knee

Articulations

Synarthroses- no movement

• suture- fibrous connective tissue binds two bones tightly together

• gomphosis- cone shaped peg in a socket (tooth in jaw)

• synchondrosis- bones connected by hyaline cartilage (epiphyseal plate)

  • becomes synostosis when calcification is complete

Amphiarthroses

• syndesmosis/ interosseous membranes- more fibers that a suture but not as tight.

  • allows slight movement

  • distal articulation of the tibia and fibula

• Symphysis- fibrous cartilage (pubic symphysis)

Diarthroses

• synovial joints- synovial cavity filled with synovial fluid

  • articular capsule and accessory ligaments (inside or outside capsule)

  • ends of bones covered with articular cartilage that has no perichondrium

  • capsule has dense fibrous outer layer

  • inner layer- synovial membrane that produces synovial fluid

  • lymph/hyaluronic acid and acts as lubricant

• Menisci/articular discs- fibrous pads between synovial joints composed of dense irregular fibrous connective tissue

• Bursae- sacs of fluid in body tissue that resemble a synovial joint without bone-to-bone articulation

  • fluid filled with inner synovial membrane and often connected to synovial cavity of a joint

  • prevent friction between the end of a bone and the surrounding soft tissue (tendons, ligaments, muscle

Synovial Joints

• planar- flat curved surfaces allow back and forth or side to side movement

  • intercarpal and intertarsal joints

• hinge- one bone with a convex surface fit into another bone with concave surface to allow an open-close movement

  • knee, elbow

• pivot- rounded or pointed surface with one bone articulates with a ring formed partly by another bone and partly by a ligament

  • radioulnar- allows palm to turn

• saddle- one bone is saddle shaped and the other bone fits like a rider in the saddle

  • between carpal bone and metacarpal of the thumb

• ball-and-socket- The rounded projection, ball, of one bone fits into depression of another bone

  • shoulder and hip

Movements

• flexion-

  • 1. decrease in the anterior angle between bones (except the knee and toes)

  • 2. bend in the anterior or posterior direction

  • 3. move out of anatomical position in the anterior or posterior direction

• extension-

  • 1. increase in the anterior angle between bones (except knee and toes)

  • 2, straighten in the anterior or posterior direction

  • 3. move to anatomical position in the anterior or posterior direction

• hyperextension- extend beyond a straight line or beyond normal range

• abduction- movement away from midline

• adduction- movement toward midline

• supination- turn palms forward (anatomical position) or up

• pronation- turn palms back or down