Articulations (Joints)

• Definition: Articulations are where bones meet, also including cartilage and teeth. Study of joints is called arthrology.

• Mobility vs. Stability: More mobility leads to less stability and vice versa.

Types of Joints

• Classification: Based on structure and function.

  • Structural:

  • Fibrous: No movement.

  • Cartilaginous: Some movement.

  • Synovial: Full movement.

  • Functional:

  • Synarthrosis: Immovable.

  • Amphiarthrosis: Slightly movable.

  • Diarthrosis: Freely movable.

Structural Classification of Joints

• Fibrous Joints: Bones joined by dense connective tissue (e.g., sutures, syndesmoses, gomphoses).

• Cartilaginous Joints: Bones joined by cartilage (e.g., synchondroses, symphyses).

• Synovial Joints: Bones separated by a fluid-filled cavity allowing free movement.

Functional Classification of Joints

• Synarthrosis: Immobile.

• Amphiarthrosis: Slightly movable.

• Diarthrosis: Freely movable.

Cartilaginous Joints

• Types:

  • Synchondroses: Hyaline cartilage (e.g., epiphyseal plate).

  • Symphyses: Fibrocartilage (e.g., pubic symphysis).

Synovial Joints

• Classes (from least to most mobile):

  1. Plane Joints

  2. Hinge Joints

  3. Pivot Joints

  4. Condylar Joints

  5. Saddle Joints

  6. Ball-and-Socket Joints

• Anatomy:

  • Joint capsule includes fibrous layer and synovial membrane.

  • Articular cartilage reduces friction and acts as a shock absorber.

  • Bursae: Sacs that reduce friction; fat pads around joints.

Major Synovial Joints

• Glenohumeral Joint: Allows for high mobility; reinforced by ligaments.

• Elbow Joint: Includes humeroulnar, humeroradial, and proximal radioulnar joints.

• Hip Joint: Secured by dense fibrous tissues.

• Knee Joint: Composed of several key ligaments (e.g., ACL, PCL) and menisci.