Joints are classified based on two primary methods: functional and structural. The key difference lies in the criteria used for classification. Functional classification considers the degree of movement allowed at the joint, while structural classification focuses on the material that binds the bones together [2].
Functional Classification
Functional joint classification categorizes joints based on the amount of movement they permit.
- Synarthrosis: Immovable joints (e.g., sutures of the skull).
- Amphiarthrosis: Slightly movable joints (e.g., intervertebral discs).
- Diarthrosis: Freely movable joints (e.g., shoulder, knee, hip). Diarthroses are most common and exhibit a wide range of motion.
Structural Classification
Structural joint classification categorizes joints based on how the bones are connected to one another [2]. There are three main types:
- Fibrous Joints: Bones are joined by fibrous connective tissue. These joints typically allow little to no movement (e.g., sutures of the skull).
- Cartilaginous Joints: Bones are joined by cartilage. These joints can allow for slight movement (e.g., intervertebral discs) or be immovable (e.g., epiphyseal plate).
- Synovial Joints: These are the most common type of joint and are characterized by a fluid-filled joint cavity. They allow for a wide range of movements (e.g., knee joint, shoulder joint).
Summary Table: Functional vs. Structural Joint Classification
| Feature | Functional Classification | Structural Classification |
|---|---|---|
| Basis | Amount of movement allowed | Material binding bones together |
| Categories | Synarthrosis, Amphiarthrosis, Diarthrosis | Fibrous, Cartilaginous, Synovial |
| Movement Allowed | Immovable, Slightly Movable, Freely Movable | Variable depending on the specific joint structure |
