In the human body, joints (or articulations) are where two or more bones meet. They are categorized based on their structure and function. Here’s a breakdown of the different types:
1. Structural Classification
This is based on what material joins the bones and whether a cavity is present:
a. Fibrous Joints
- Structure: Bones joined by dense connective tissue.
- Movement: Generally immovable (synarthroses).
- Examples:
- Sutures in the skull
- Syndesmoses (e.g., between the tibia and fibula)
- Gomphoses (e.g., teeth in their sockets)
b. Cartilaginous Joints
- Structure: Bones connected by cartilage.
- Movement: Slightly movable (amphiarthroses).
- Examples:
- Intervertebral discs
- Pubic symphysis
- Epiphyseal plates in growing children
c. Synovial Joints
- Structure: Bones separated by a fluid-filled joint cavity.
- Movement: Freely movable (diarthroses).
- Examples:
- Knee
- Shoulder
- Elbow
- Hip
2. Functional Classification
This is based on how much movement the joint allows:
a. Synarthrosis
- Immovable joints
- Examples: Skull sutures
b. Amphiarthrosis
- Slightly movable joints
- Examples: Intervertebral joints, pubic symphysis
c. Diarthrosis
- Freely movable joints (all synovial)
- Examples: Shoulder, hip, fingers
3. Types of Synovial Joints (Based on Movement)
These are the most common and most mobile:
| Type | Description | Example |
|---|---|---|
| Ball-and-socket | Multiaxial movement (rotation, flexion, etc.) | Shoulder, hip |
| Hinge | Flexion and extension | Elbow, knee |
| Pivot | Rotation around a single axis | Atlantoaxial joint (neck) |
| Saddle | Biaxial movement with more freedom than condyloid | Thumb joint (carpometacarpal) |
| Condyloid (Ellipsoidal) | Biaxial movement | Wrist joint |
| Plane (Gliding) | Sliding or gliding motions | Between tarsal bones in foot |