Structural classification

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Structural classification

• Fibrous
• Fibrous joints connect bones without allowing
  any movement. The bones of your skull and pelvis
  are held together by fibrous joints. The union of
  the spinous processes and vertebrae are fibrous
  joints.
• Cartilaginous
• Cartilaginous joints are joints in which the
  bones are attached by cartilage. These joints
  allow for only a little movement, such as in the
  spine or ribs.
• Synovial
• Synovial joints allow for much more movement
  than cartilaginous joints. Cavities between bones
  in synovial joints are filled with synovial
  fluid. This fluid helps lubricate and protect the
  bones. Bursa sacks contain the synovial fluid.

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Functional classification

• Functionally, joints can be classified as
• Synarthrosis - permit no movement.
• Amphiarthrosis - permit little movement.
• Diarthrosis - permit a variety of movements (e.g.
  flexion, adduction and pronation). Only synovial
  joints are diarthrosis.

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Synarthrosis

• Synarthroses are joints with very little (if
  any) mobility. They can be categorised by how the
  two bones are joined together
• Syndesmoses are joints where the two bones are
  joined by one of more ligaments.
• Synchondroses are joints where the two bones are
  joined by a piece of cartilage.
• Synostoses are the fusion of two bones, to the
  point that they are practically one bone. In
  humans, the plates of the cranium, initially
  separate, fuse together as the child approaches
  adulthood.

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Diarthroses

• Diarthroses (sometimes called synovial joints and
  also diarthroidal joints) are the most common and
  most moveable type of joint in the body.
• The whole of a diarthrosis is contained by a
  ligamentous sac called the articular capsule.
• The surfaces of the two bones at the joint are
  covered in cartilage. The thickness of the
  cartilage varies with each joint, and sometimes
  may be of uneven thickness. Articular cartilage
  is multi-layered. A thin superficial layer
  provides a smooth surface for the two bones to
  slide against each other. In joints where the two
  surfaces do not fit snugly together, a meniscus
  or multiple folds of fibro- cartilage within the
  joint correct the fit, ensuring stability and the
  optimal distribution of load forces.
• The synovium is a membrane that covers all the
  non-cartilaginous surfaces within the articular
  capsule. It secretes synovial fluid into the
  joint, which nourishes and lubricates the
  articular cartilage. The synovium is separated
  from the capsule by a layer of celluar tissue
  that contains blood vessels and nerves.

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Grouping Joints by appearance

• Hinge A hinge joint allows extension and
  retraction of an appendage.
• Saddle A saddle joint allows movement back and
  forth and up and down, bot does not allow for
  rotation like a ball and socket joint.

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Grouping Joints by appearance

• Ball and Socket A ball and socket joint allows
  for radial movement in almost any direction. They
  are found in the hips and shoulders.
• Pivot
• Pivot joints allow rotation around an axis. The
  neck and forearms have pivot joints. In the neck
  the occipital bone spins over the top of the
  axis. In the forearms the radius and ulna twist
  around each other.

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Grouping Joints by appearance

• Ellipsoid
• Ellipsoid joints are similar to a ball and
  socket joint. They allow the same type of movment
  to a lesser magnitude. The wrist is an ellipsoid
  joint.
• Pivot
• Pivot joints allow rotation around an axis. The
  neck and forearms have pivot joints. In the neck
  the occipital bone spins over the top of the
  axis. In the forearms, the radius and ulna twist
  arround each other.

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References and Sources

• http//en.wikipedia.org/wiki/Joints
• http//www.shockfamily.net/skeleton/JOINTS.HTML