Joint Classification and Characteristics

Structural Class of Joints

Fibrous Joints

• Structural Characteristics:

  • Bones are united by collagen fibers.

• Types of Fibrous Joints:

  • Suture:

  • Characterized by short fibers.

  • Found only in the skull.

  • Syndesmosis:

  • Joint held together by a ligament.

  • Fibrous tissue can vary in length but is generally longer than in sutures.

  • Gomphosis:

  • Peg-in-socket joint, where a tooth is held in its socket by the periodontal ligament.

Cartilaginous Joints

• Structural Characteristics:

  • Adjoining bones united by cartilage.

  • No joint cavity present.

  • Not highly movable.

• Types of Cartilaginous Joints:

  • Synchondrosis:

  • Bones united by hyaline cartilage (e.g., epiphyseal plate).

  • Symphysis:

  • Bones united by fibrocartilage.

  • Examples include intervertebral discs and pubic symphysis.

Synovial Joints

• Structural Characteristics:

  • Adjoining bones covered with articular cartilage.

  • Separated by a joint cavity.

  • Enclosed within an articular capsule lined with synovial membrane.

• Types of Synovial Joints:

  • Plane:

  • Condylar:

  • Hinge:

  • Pivot:

  • Saddle:

  • Ball-and-socket:

• Mobility of Synovial Joints:

  • Freely movable (diarthrosis); movements depend on the design of the joint.

Functional Classifications of Joints

• Classification Based on Movement: - Synarthroses:

  • Immovable joints.

  • Amphiarthroses:

  • Slightly movable joints.

  • Diarthroses:

  • Freely movable joints.

Fibrous Joints Details

• Characteristics: - Composed of dense fibrous connective tissue with no joint cavity.

  • Most fibrous joints are immovable, though mobility can depend on the length of connective tissue fibers.

Types of Fibrous Joints Explained

• Suture (a):

  • Joints are held together with very short interconnecting fibers, and bone edges interlock.

  • Found only in the skull, allowing for growth in youth.

  • Contain short connective tissue fibers that allow for expansion.

  • Ossify and fuse in middle age, resulting in immovable conditions referred to as synostoses.

• Syndesmosis (b):

  • Joint held together by a ligament.

  • Fibrous tissue can vary in length and is longer than in sutures.

• Gomphosis (c):

  • Described as a peg-in-socket joint, where a tooth is held in its socket by the periodontal ligament.