Joint Facts

  • Body joints are places where bones meet.
  • The skull is not one bone, but 22 separate bones bound tightly together with fibers so that they cannot move.
  • Most body joints (apart from fixed joints like the skull’s fibrous joints) let bones move, but different kinds of joint let them move in different ways.
  • Hinge joints, such as the elbow, let the bones swing to and fro in two directions like door hinges do.
  • In ball-and-socket joints, such as the shoulder and hip, the rounded end of one bone sits in the cup shaped socket of the other, and can move in almost any direction.
  • Swivel joints turn like a wheel on an axle. Your head can swivel to the left or to the right on your spine.
  • Saddle joints such as those-in the thumb have the bones interlocking like two saddles. These joints allow great mobility with considerable strength.
  • The relatively inflexible joints between the bones (vertebrae) of the spine are cushioned by pads of cartilage.
  • Synovial joints are flexible joints such as the hip-joint, lubricated with oily ‘synovial fluid’ and cushioned by cartilage.