Bones L03

3. Describe the classification of joints. Discuss the basic characteristics of the three types of joints.

Joints classification schemes are often very specific to discipline, but two major means of classification are common: joint structure & range movement allowed. You are responsible for knowing classification based on joint structure.

With this scheme, joints are classified according to the type of tissue that unites the articulating bones and how the tissue attaches the bones. There are 3 main types:

In fibrous joints, bones are joined by fibrous connective tissue, and the degree of movement depends on the length of fibers uniting the bones.

    • Examples include:
      • Sutures -- little movement
      • Syndesmosis -- degree of movement depends on the distance between the bones [e.g. interosseous membrane]
      • Gomphosis – unique joint between a tooth and the bone

In cartilaginous joints, the surfaces of the articulating bones are covered with hyaline cartilage (articular cartilage), and bones are united by strong fibrous tissue and/or fibrocartilage. These joints tend to be strong and slightly moveable.

    • Examples include:
      • Epiphyseal growth plate
      • Intervertebral discs
      • Pubic symphysis
      • Manubriosternal joint

Synovial joints are unique in that bones are connected via an articular capsule rather than a continuous sheet of connective tissue. This organization allows for free movement between bones.

All synovial joints have:

    • Articular (synovial) capsule
      • There are 2 parts of the capsule: an outer fibrous layer and the inner synovial membrane, which secretes synovial fluid.
    • Articular (synovial) cavity
      • Synovial fluid lines the majority of the cavity
    • Articular cartilage (hyaline cartilage)
      • Mostly avascular and slow/does not heal