Joints

Different Kinds of Joints Your skeleton is made up of bones. Joints are where the bones meet. They are divided into three types depending on how freely the bones can move. Fixed or immoveable Slightly moveable Freely moveable/Synovial

Fixed or Immoveable Joints The bones at an immoveable joint cant move at all. They interlock or overlap, and are held close together by tough fibre. The joints between the plates in the cranium are a good example. Examples are in the cranium and sacrum.

Gaps called fontanelles between plates in the cranium allow a baby’s head to squash during birth. Twelve months later the gaps will have closed and fixed joints will have started to form.

Slightly Moveable Joints They only allow a little bit of movement. They are held together by strong white cords or straps called ligaments and joined by cartilage. Cartilage is a gristly cushion which is on the ends of bone and stops them from wearing away. The joints in your vertebrae are slightly moveable. It has cartilage pads between them which act as shock absorbers so the bones won’t jar when you run and jump. Other examples include the joints between your ribs and sternum. These move a little when you breathe in and out.

Freely Moveable Joints They can move quite freely. (knee joint) A freely moveable joint has these parts: Joint Capsule Synovial membrane with synovial fluid Joint cavity Cartilage Ligaments They are also called synovial joints.

Cartilage & Ligaments Cartilage – protects bones and stops them knocking together. It forms a gristly cushion between bones at slightly moveable joints. Ligaments – connect bone to bone. They are elastic enough to allow movement. Too much movement and they would tear your flesh.

Synovial Joints

Using joint sheet!! The ball-and-socket joint Most moveable joint. One bone has a bulge like a ball at the end. This fits into a socket in the other bone. It can turn in many directions (hip/shoulder).

The Hinge Joint Works like a hinge on a door. The bone can swing back and forward. The end of one bone is shaped like a spool of thread and fits into a hollow in the other. The joint opens until straight, but no further. (elbow/knee)

The Pivot Joint One bone has a bit that juts out, like a peg or a ridge. This fits into a ring or notch on the other bone. The joint only allows rotation. (neck) The Saddle Joint The ends of the bone are shaped like saddles and fit snugly together. It allows movement back and forward and from side to side (thumb).

The Condyloid Joint A rounded bump on one bone sits in a hollow formed by another bone or bones. The joint allows movement back and forward and from side to side. Ligaments prevent bones from rotating (joint at wrists)

The Gliding Joint Here the ends of the bones are flat enough to glide over each other. There is little movement in all directions. This joint gives the least amount of movement (carpals/tarsal in the hand and foot).

Joint Movements

Movement Definition Example Sport Situation Flexion Bending a part of your body. Extension Straightening a part of your body. Abduction A sideways movement of a limb away from your body. Adduction A sideways movement towards the centre line of your body. Rotation Turning movement around an imaginary line. Circumd-uction End of a bone moving in a circle.