Classification of Articulations: Functional and Structural Types

Classification of Articulations

Articulations, or joints, are connections between bones that allow for varying degrees of movement. They are classified both by their function (the amount of movement they allow) and by their structure (the material connecting the bones and the presence or absence of a joint cavity).

Functional Classification of Joints

• Synarthrosis: Immovable joints

• Amphiarthrosis: Slightly movable joints

• Diarthrosis: Freely movable joints

Structural Classification of Joints

• Fibrous Joints: Bones joined by dense connective tissue

• Cartilaginous Joints: Bones joined by cartilage

• Synovial Joints: Bones separated by a fluid-filled joint cavity

Functional and Structural Categories of Joints

Functional Category	Structural Category & Type	Description & Examples
Synarthrosis (No Movement)	Fibrous: Suture	Found only between bones of the skull. The edges of the bones are interlocked and bound together by dense fibrous connective tissue.
	Fibrous: Gomphosis	Binds the teeth to bony sockets in the maxillae and mandible. The fibrous connection is the periodontal ligament.
	Cartilaginous: Synchondrosis	A rigid, cartilaginous bridge between two articulating bones. Example: The connection between the ends of the first pair of vertebrosternal ribs and the sternum.
	Bony Fusion: Synostosis	A totally rigid, immovable joint created when two bones fuse and the boundary between them disappears. Examples: The frontal suture of the frontal bone and the epiphyseal lines of mature long bones.
Amphiarthrosis (Little Movement)	Fibrous: Syndesmosis	Bones are connected by a ligament. Example: The distal articulation between the tibia and fibula.
	Cartilaginous: Symphysis	The articulating bones are separated by a wedge or pad of fibrous cartilage. Example: The pubic symphysis between the two pubic bones.
Diarthrosis (Free Movement)	Synovial	Permit a wide range of motion. Typically located at the ends of long bones (e.g., upper and lower limbs). Monaxial: Movement in one plane (e.g., elbow, ankle) Biaxial: Movement in two planes (e.g., ribs, wrist) Triaxial: Movement in three planes (e.g., shoulder, hip)

Key Terms and Definitions

• Suture: An immovable fibrous joint found only in the skull.

• Gomphosis: A fibrous joint that anchors a tooth to its socket.

• Synchondrosis: A cartilaginous joint where bones are joined by hyaline cartilage.

• Synostosis: A bony fusion where two bones become one.

• Syndesmosis: A fibrous joint where bones are connected by a ligament.

• Symphysis: A cartilaginous joint where bones are separated by fibrocartilage.

• Synovial Joint: A freely movable joint with a synovial cavity.

Examples and Applications

• Sutures stabilize the skull and protect the brain.

• Gomphoses secure teeth, allowing for effective chewing.

• Synchondroses are important in the growth of long bones during development.

• Synostoses mark the end of bone growth (e.g., epiphyseal lines).

• Syndesmoses provide slight movement and stability between long bones.

• Symphyses absorb shock and allow for limited movement (e.g., during childbirth at the pubic symphysis).

• Synovial joints enable complex movements necessary for locomotion and manipulation.

Additional info:

• Synovial joints are characterized by the presence of a joint cavity filled with synovial fluid, articular cartilage, and a joint capsule.

• Movement at synovial joints is described by the number of axes (monaxial, biaxial, triaxial) along which movement occurs.