Articulations: Types, Movements, and Key Joints

Major types of joints

  • Fibrous joints: sutures (skull), syndesmoses (interosseous membranes), gomphoses (tooth sockets)
  • Cartilaginous joints: synchondroses (epiphyseal plates, costochondral joints), symphyses (pubic symphysis, intervertebral discs)
  • Synovial joints: features
    • Diarthrotic joints with a synovial cavity
    • Articular cartilage on bone ends
    • Joint capsule enclosing the cavity
    • Synovial membrane and fluid
    • Reinforcing ligaments; may include discs/menisci and bursae
  • Synovial joint subtypes (based on shape/movement):
    • ball-and-socket
    • hinge
    • pivot
    • condyloid
    • saddle
    • plane

Movements allowed by joints

  • Degrees of freedom
    • Uniaxial: hinge, pivot
    • Biaxial: condyloid, saddle
    • Multiaxial: ball-and-socket
  • Common movements
    • Flexion / Extension
    • Abduction / Adduction
    • Medial (internal) rotation / Lateral (external) rotation
    • Circumduction
    • Forearm rotation: Pronation / Supination (via radioulnar joints)
  • Shoulder and hip (ball-and-socket): Flexion, Extension, Abduction, Adduction, Medial rotation, Lateral rotation, Circumduction
  • Knee (modified hinge): Flexion, Extension; slight rotation when flexed
  • Elbow (hinge): Flexion, Extension; forearm rotation via proximal radioulnar joint

Structural features: Shoulder (glenohumeral)

  • Type: ball-and-socket synovial joint
  • Articulations: head of humerus with glenoid cavity of scapula
  • Stability/support: loose joint capsule; rotator cuff tendons; glenoid labrum; glenohumeral ligaments
  • Additional structures: acromion process, coracoid process; subacromial space
  • Movements: Flexion, Extension, Abduction, Adduction, Medial rotation, Lateral rotation, Circumduction

Structural features: Hip (coxal)

  • Type: ball-and-socket synovial joint
  • Articulations: femoral head with acetabulum
  • Stability/support: deep socket; strong capsule; ligaments (iliofemoral, pubofemoral, ischiofemoral); labrum
  • Additional structures: surrounding muscles and capsule
  • Movements: Flexion, Extension, Abduction, Adduction, Medial rotation, Lateral rotation, Circumduction

Structural features: Knee

  • Type: primarily a hinge-like synovial joint (femorotibial) with a separate patellofemoral articulation
  • Surfaces: femoral condyles, tibial plateau, patella
  • Stabilizers: cruciate ligaments (ACL, PCL); collateral ligaments (MCL, LCL); menisci
  • Capsule and bursae: joint capsule; associated bursae
  • Movements: Flexion, Extension; slight rotation when flexed; patellofemoral tracking

Structural features: Elbow

  • Type: hinge joint (humero-ulnar) plus proximal radioulnar articulation for rotation
  • Articulations: trochlea of humerus with ulna trochlear notch; radius head with capitulum; proximal radioulnar joint
  • Stability features: joint capsule; ulnar collateral and radial collateral ligaments; annular ligament
  • Key structures: olecranon process and olecranon fossa
  • Movements: Flexion, Extension; Forearm rotation (Pronation / Supination) via radioulnar joints