Joints: Definition, Functions, and Types

Definition of Joints

• A joint is a connection between two or more bones
• Joints hold bones together
• Joints allow movement
• Joints provide space for bone growth

Function of Joints

• Allow for movement
• Provide space for bone growth
• Hold bones together

Types of Joints

• Fibrous Joints: bones are connected by fibrous tissue, allow minimal or no movement
  • Examples: Sutures of the skull, Syndesmoses (between tibia & fibula, radius and ulna), Gomphoses (teeth in sockets)
• Cartilaginous Joints: bones are joined by cartilage
  • Primary Cartilaginous Joint (Synchondroses): united by hyaline cartilage, no movement, temporary joints found in growing bones
    • Example: Epiphyseal cartilage in long bones
  • Secondary Cartilaginous Joint (Symphysis): united by fibrocartilage, small amount of movement
    • Example: Joints between vertebral bodies, symphysis pubis
• Synovial Joints: allow a wide range of movement
  • Structure:
    • Articular surfaces covered by hyaline cartilage
    • Articular cavity (joint space)
    • Synovial fluid
    • Fibrous capsule: surrounds the joint, synovial membrane lines the capsule and non-articulating surfaces

Classification of Synovial Joints

• Plane or Gliding Joint: Flat or almost flat articular surfaces, allows bones to slide on each other
  • Example: Between carpals, tarsals
• Hinge Joint: Resembles a door hinge, allows flexion and extension
  • Example: Elbow, knee, ankle, joints between phalanges
• Pivot Joint: Central bony pivot surrounded by a ligamentous ring, allows rotation
  • Example: Atlantoaxial, superior radioulnar joints
• Condyloid Joint: Convex surface articulates with a concave surface
  • Example: Wrist, metacarpophalangeal joints
• Saddle Joint: Concavo-convex articular surfaces resembling a saddle, allows a variety of movements
  • Example: Carpometacarpal joint of the thumb
• Ball and Socket Joint: Ball-shaped head of one bone fits into a socket-like concavity of another, allows free movement in all directions
  • Example: Shoulder, hip joints

Joints in the Human Body

• Skull:
  • Sutures (between skull bones)
  • Temporo-mandibular (between skull and mandible)
• Vertebral Column:
  • Intervertebral (between vertebrae)
  • Atlanto-axial (between C1 and C2 vertebrae)
• Chest:
  • Sterno-clavicular
  • Sterno-costal (between sternum and ribs)
  • Shoulder joint
  • Elbow
  • Superior Radio-ulnar
  • Inferior Radio-ulnar
• Hand:
  • Wrist
  • Intercarpal
  • Carpo-metacarpal
  • Metacarpo-phalangeal
  • Interphalangeal
• Pelvis:
  • Sacro-iliac
  • Symphysis pubis
  • Hip
  • Knee
• Lower Limb:
  • Superior Tibio-fibular
  • Inferior Tibio-fibular
  • Ankle
  • Intertarsal
  • Subtalar
  • Tarso-metatarsal
  • Interphalangeal