Joint Classifications and Movement Fundamentals

Joint Classifications

  • Synarthroses: immovable

    • Examples: sutura, schindylesis, gomphosis (teeth), and synchondrosis

  • Amphiarthroses: slightly movable

    • Example: articulations between the vertebrae

  • Diarthroses (synovial joints): freely movable

    • Examples: hinge joint, pivot joint, ellipsoid (condyloid), saddle joint, ball-and-socket joints, and gliding joints

Diarthrodial Joint Structures

  • Elements ALWAYS associated with diarthrodial joints:

    • Synovial fluid

    • Articular cartilage

    • Articular capsule (fibrous capsule)

    • Synovial membrane

    • Capsular ligaments

    • Blood vessels

    • Nerve

    • Muscle around the joint

    • Synovial fluid (reiterated for emphasis)

    • Meniscus

  • Elements SOMETIMES associated with diarthrodial joints:

    • Intraarticular discs or menisci

    • Peripheral labrum

    • Fat pads

    • Synovial plicae

    • Fat pad

  • Joints that allow motion have structures that both control motion and prevent friction between joint surfaces:

    • Bursa

    • Tendon

Diarthrodial Joint Examples and Degrees of Freedom (DOF)

  • Pivot Joint

    • 1° of freedom, Pronation and Supination

    • Example component: Annular ligament around the Radius

  • Ellipsoid (Condyloid) Joint

    • 2° of motion: Flex/Ext and Radial/Ulnar deviation

    • Example region: Radius-Ulna region (wrist context: radiocarpal area)

  • Hinge Joint

    • 1° of freedom, Flexion and Extension

    • Example: Humerus–Ulna (elbow)

  • Gliding (Arthrodial) Joints

    • e.g., Scaphoid–Lunate (carpal joints)

  • Ball-and-socket Joint

    • 3° of freedom

    • Planes of motion: Sagittal, Frontal (Coronal), and Transverse (Horizontal)

Terms to Describe Motion

  • Flexion / Extension

  • Abduction / Adduction

  • Internal / External Rotation

  • Ulnar Deviation / Radial Deviation

  • Inversion / Eversion

  • Dorsiflexion / Plantarflexion

Planes of Motion and DOF Context

  • Ball-and-socket joints provide 3∘3^{\circ} of freedom

  • Planes of motion:

    • Sagittal

    • Frontal (Coronal)

    • Transverse (Horizontal)

Motion Restrictions and ROM

  • To restore motion, clinicians must understand:

    • Factors that influence normal motion

    • Factors that contribute to motion restrictions

  • Impairment can lead to disability and may cause further pathology

  • Without pathology, normal ROM is generally limited by lengthening or approximation of anatomical structures

Elbow and Shoulder Movement Notes

  • Elbow extension is limited by bone approximation (bone-on-bone contact)

  • Elbow flexion is limited by soft tissue approximation

  • Motion can be limited by soft tissue distension

  • Extra-articular accessory motion: upward rotation of the scapula accompanies shoulder flexion