Articulations                           Slide Presentation

      Since the bones are hard, inflexible structures, movement can only occur at joints where two bones interconnect. There are three main joint categories distinguished by the degree of movement permitted. Each of these categories is further subdivided on the basis of the nature of the material found within the joint.

A.  Synarthrosis – an immoveable joint.

  1. Fibrous – bones are held together by dense fibrous connective tissue. Examples are:
    1. Suture – a joint commonly seen in the skull holding cranial bones together.
    2. Gomphosis – a joint between the teeth and the bony sockets. The fibrous connection between the tooth and socket is called a periodontal ligament.

       2.  Cartilagenous – bones are held together immoveably with cartilage. For example, a synchondrosis is a rigid          cartilagenous plate between the epiphysis and diaphysis of a long bone – the epiphyseal growth plate.

B.  Amphiarthrosis – a slightly moveable joint.

  1. Fibrous – bones are held together by a fibrous ligament or sheet. For example, a syndesmosis holds the distal ends of the tibia and fibula together. A fibrous sheet, the interosseous membrane, holds the tibia and fibula, as well as, the radius and ulna together.
  2. Cartilagenous – articulating bones are held together by a pad of fibrocartilage. Examples include the symphysis, a cartilagenous, amphiarthrotic joint holding together the coxal bones at the pubis. This type of joint is also found between the bodies of the vertebrae – the intervertebral disks.

C.  Diarthrosis – a freely moveable joint always showing a joint capsule lined with a synovial membrane. The synovial joints are further subdivided by the type of movement they allow:

  1. Monaxial – movement in one plane (knee and elbow).
  2. Biaxial – movement in two planes (wrist and ribs)
  3. Triaxial – movement in three planes (shoulder and hip)