Understanding Joints

Also called an "articulation," joints connect bones throughout the body. Some joints connect bones without allowing movement. These are called fibrous joints and are found in the skull, pelvis and spinal cord. Cartilaginous joints allow only a small amount of movement and are found in the ribs and spine. Bones at these joints are attached by cartilage.

And synovial joints allow a broader range of movement and represent many of the joints connecting bones in the hand and upper extremity. Also called diarthrosis joints, these joints are filled with synovial fluid, which lubricates and protects bones. Synovial joints also provide stability, bear weight and nourish cartilage. A Bursa sack holds the synovial fluid in these joints.

There are six types of synovial joints

  • Hinge - allows extension and retraction and is the kind of joint found in the elbow and knee, as well as the middle and distal phalanges of the fingers and toes.
  • Ball and Socket - allows the greatest range of motion such as that found in the shoulder, where the long arm bone connects at the shoulder blade.
  • Pivot - allows one bone to rotate around another and is the type of joint found in the neck.
  • Saddle - allows for up and down and back and forth movement and is the type of joint only found in the thumb.
  • Condyloid or ellipsoid - allows a smaller range of ball and socket type of rotation and is the type of joint found in the distal radius area of the wrist.
  • Gliding - allows bones to slide past one another and are the types of joints found in the midcarpal region of the hand and wrist.