Courtesy: Andrew Dixon MD
Radiologist
Alfred Health
Melbourne, Australia

and Radiopedia
www.radiopaedia.org

 

Types of Joints: Anatomic and Radiologic Correlation

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Definition

• A joint (articulation) is a site where two or more bones meet
• Functions:
  • Provide stability
  • Allow movement
  • Offer mechanical support

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Additional Note

• Some joints are temporary (during skeletal development)
• Most joints persist in the adult skeleton

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Structural Classification of Joints

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Three Main Types

1. Fibrous joints
2. Cartilaginous joints
3. Synovial joints

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1. Fibrous Joints

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Definition

• Bones connected by dense fibrous connective tissue (collagen-rich)

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Movement

• Minimal or none

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Functional Type

• Synarthrosis

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Types of Fibrous Joints

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1. Sutures

• Found in skull

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Examples

• Coronal suture
• Sagittal suture
• Lambdoid suture

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Features

• Immovable
• Short fibrous connections

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2. Syndesmosis

• Bones connected by:
  • Ligaments
  • Interosseous membrane

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Examples

• Distal tibiofibular joint
• Interosseous membrane (radius–ulna)

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Movement

• Slight

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Clinical Correlation

• Syndesmotic injury:
  • Seen in Weber C ankle fractures
  • Features:
    • Widened ankle mortise
    • Instability
  • Often requires surgical fixation

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3. Gomphosis

• Peg-and-socket joint

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Example

• Tooth in alveolar socket

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2. Cartilaginous Joints

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Definition

• Bones connected entirely by cartilage

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Movement

• Limited

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Types

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1. Primary Cartilaginous Joints (Synchondrosis)

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Structure

• Hyaline cartilage

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Features

• Often temporary
• Seen in growing skeleton

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Examples

• Epiphyseal (growth) plate
• Apophysis (e.g., greater trochanter)
• Triradiate cartilage

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Adult Examples

• Petro-occipital synchondrosis
• First sternocostal joint

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Pathological Example

• Calcaneonavicular coalition

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2. Secondary Cartilaginous Joints (Symphysis)

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Structure

• Fibrocartilage

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Movement

• Slight

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Functional Type

• Amphiarthrosis

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Examples

• Pubic symphysis
• Intervertebral discs
• Manubriosternal joint

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Intervertebral Disc Components

• Annulus fibrosus
• Nucleus pulposus

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3. Synovial Joints

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Definition

• Bones connected by a joint capsule containing synovial fluid

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Movement

• Freely movable

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Functional Type

• Diarthrosis

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Components

1. Articular cartilage (hyaline)
2. Joint capsule
3. Synovial membrane
4. Synovial fluid
5. Joint cavity

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Important Clarification

• Synovial joints contain cartilage but are not cartilaginous joints

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Types of Synovial Joints

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1. Ball-and-Socket Joint

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Structure

• Spherical head + cup-shaped socket

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Movements

• Flexion / extension
• Abduction / adduction
• Rotation
• Circumduction

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Examples

• Hip joint
• Shoulder joint

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2. Condyloid Joint

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Structure

• Oval surface + elliptical cavity

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Movements

• Flexion / extension
• Abduction / adduction
• Circumduction

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Limitation

• No rotation

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Examples

• Radiocarpal joint
• Metacarpophalangeal joints

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3. Saddle Joint

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Structure

• Reciprocal concave-convex surfaces

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Movements

• Flexion / extension
• Abduction / adduction
• Circumduction

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Example

• First carpometacarpal joint

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4. Hinge Joint

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Structure

• Convex surface + concave surface

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Movement

• One axis:
  • Flexion
  • Extension

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Examples

• Elbow joint
• Interphalangeal joints

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Modified Hinges

• Knee
• Ankle

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5. Pivot Joint

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Structure

• Rotation within ligamentous ring

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Movement

• Rotation around longitudinal axis

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Examples

• Atlantoaxial joint
• Proximal radioulnar joint
• Distal radioulnar joint

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6. Plane Joint

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Structure

• Flat surfaces

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Movement

• Gliding

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Examples

• Intercarpal joints
• Intertarsal joints
• Facet joints
• Acromioclavicular joint

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Degrees of Freedom

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Functional Classification

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Summary

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Fibrous Joints

• Sutures
• Syndesmosis
• Gomphosis
• Movement: Minimal or none

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Cartilaginous Joints

• Synchondrosis (hyaline cartilage)
• Symphysis (fibrocartilage)
• Movement: Limited

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Synovial Joints

• Have:
  • Joint capsule
  • Synovial fluid
  • Articular cartilage
• Movement: Free