Types of Joints in Human Body

Support & Movement

• Movement occurs at joints where two bones connect
• Joint structure dictates the direction and range of motion possible
• Joint strength decreases as mobility increases

Articulations (Joints)

• Joints are locations where bones connect
• Joint type influences the degree and direction of movement a joint allows.

Classification of Joints

• Functional Classification:
  • Synarthrosis: immovable joints (e.g., suture in the skull)
  • Amphiarthrosis: slightly movable joints (e.g., symphysis pubis)
  • Diarthrosis: freely movable joints (e.g., synovial joints)
• Structural Classification:
  • Bony: bones fused together (e.g., metopic suture)
  • Fibrous: connected by fibrous connective tissue (e.g., sutures in the skull)
  • Cartilaginous: connected by cartilage (e.g., synchondroses)
  • Synovial: contains a synovial cavity (e.g., shoulder, knee)

Synarthrosis

• Immovable joints
• Very strong
• Edges of bones may touch or interlock
• Types:
  • Suture (fibrous): interlocking bones bound by dense fibrous connective tissue (only in the skull)
  • Gomphosis (fibrous): binds teeth to sockets with fibrous connective tissue
  • Synchondrosis (cartilaginous): rigid cartilaginous bridge between bones (e.g., epiphyseal cartilage, between ribs and sternum)
  • Synostosis (bony): fused bones (e.g., metopic suture in the skull, epiphyseal lines in adults)

Amphiarthrosis

• Slightly movable joints
• Types:
  • Syndesmosis: bones connected by ligaments (e.g., superior and inferior tibiofibular joints)
  • Symphysis: bones connected by fibrocartilage (e.g., intervertebral discs, symphysis pubis)

Diarthroses (Synovial Joints)

• Freely movable joints
• Found at ends of long bones
• Components:
  • Joint capsule
  • Synovial membrane
  • Articular cartilage
  • Synovial fluid (lubricates the joint)
• Accessory Structures:
  • Menisci (cartilages) cushion the joint.
  • Fat pads, superficial to the joint capsule
  • Ligaments, support and strength
  • Tendons, attach to muscles around the joint
  • Bursae (fluid-filled pockets) cushion areas where tendons or ligaments rub

Dynamic Motions

• Types:
  • Linear motion (gliding)
  • Angular motion
  • Circumduction
  • Rotation
• Terms of movements describe: Plane or direction of motion, and relationships between structures.

Flexion and Extension, Dorsiflexion & Plantar Flexion, Adduction & Abduction, Circumduction, Rotation, Inversion & Eversion, Mandibular Movements, Opposition

• These are examples of specific types of movement at joints

Intervertebral Articulations

• Vertebral column articulations:
• C2 to L5 vertebrae have synovial joints (diarthroses) between superior and inferior articular processes
• Adjacent vertebral bodies are connected by amphiarthrosis joints (symphyses) via intervertebral discs

Intervertebral Discs

• Pad of fibrocartilage separating vertebral bodies
• Structure:
  • Annulus fibrosus: tough outer layer connecting the disc to the vertebrae
  • Nucleus pulposus: elastic, gelatinous core absorbing shocks

Damage to Intervertebral Discs

• Slipped disc: bulge in the annulus fibrosus, may invade the vertebral canal
• Herniated disc: nucleus pulposus breaks through the annulus fibrosus, puts pressure on spinal cord or nerves

Intervertebral Ligaments

• Stabilize the vertebral column
• Several ligaments bind vertebrae together

Shoulder Joint

• Multiaxial ball-and-socket synovial joint
• Highest mobility, least stability
• Between head of humerus and glenoid cavity of scapula

Elbow Joint

• Monoaxial hinge synovial joint
• Between humerus, radius, and ulna
• Stable joint

Hip (coxal) Joint

• Multiaxial ball-and-socket synovial joint.
• Between head of femur and acetabulum of hip bone.
• Strong joint with wide range of motion.

Knee Joint

• Monoaxial hinge synovial joint.
• Complicated joint transferring weight from femur to tibia.
• Articulations:
  • 2 femur-tibia articulations at medial and lateral condyles
  • 1 between patella and patellar surface of femur

Menisci of the Knee

• Medial and lateral fibrocartilage pads cushion and stabilize joint.

Ligaments of the Knee

• Several ligaments help stabilize the knee joint

Common Clinical Problems

• Joint Injuries:
  • Dislocation (luxation): articulating surfaces forced out of position
  • Subluxation: partial dislocation
• Rheumatism: non-specific term for pain and stiffness of skeletal and muscular systems
• Arthralgia: pain in one or more joints
• Arthritis: Inflammation of a joint
  • Causes infectious, autoimmune, metabolic
  • Examples rheumatoid arthritis, gouty arthritis
• Osteoarthritis: Non-inflammatory degenerative joint disease
  • Pathology: cartilage breakdown allowing bones to rub together

Factors Affecting Bone Strength

• Age
• Physical stress
• Hormone levels
• Calcium and phosphorus uptake and excretion
• Genetic and environmental factors

Effect of Aging on Skeletal System

• Decreased bone mass
• Bones weaken
• Increased risk of fractures and dislocations
• Degeneration of articular surfaces

Integration of Skeletal System with Other Systems

• The skeletal system supports and protects other systems.
• Stores minerals needed for other systems.
• Provides blood cell production.

Effects of Disorders on Skeletal System

• Disorders in other body systems can cause bone tumors, osteoporosis, arthritis, and demineralization