Introduction to Osteology & Arthrology

active movement anatomy arthrology ball and socket bone bone tissue bursae cartilanginous condyloid ellipsoid endosteum fibrous capsule fibrous joints flat bones functions of bone gomphosis hinge human skeleton hyaline cartilage irregular bones joint cavity joint movement ligaments long bones osteology passive movement peristeum pivot sesamoid bones short bones spongy bone suture synchondrosis syndesmosis synovial fluid synovial joints synovial membrane trabecular

Osteology Arthrology physiotherapy solihull simon evans

Introduction to Osteology

  • The Human Skeleton
    • Bilaterally Symmetrical
    • Endoskeleton
    • Divided into axial skeleton - vertebral column, skull, ribs and sternum
    • …and Appendicular Skeleton - pectoral and pelvic girdles and bones of Upper Limb & Lower Limb

Bone Tissue

  • Bones differ macroscopically but are similar microscopically
  • Bone tissues are classified as a specialised form of Connective Tissue and consists of a blend of:
    • Organic components
      • Collagen - provides pliability and resists tensile forces
      • Cells - continual building and resorption of bone tissue
  • Inorganic components:
    • Ca salts provide rigidity and compressive strength
  • Microscopic appearance may vary with age - balance of organic and inorganic content changes….
  • (Young bones - not yet mineralised - pliable / Old bones - mineralised tissue mass - weak & brittle)
  • All bones are formed from differing amounts of connective tissues
    • Perosteum - external fibrous tissue covering for nutrition and attachment of soft tissue structures
    • Endosteum - loose areolar tissue found in cavities of some bones
  • Bone Tissue Proper:
    • Compact bone - dense, hard layer of bone (external)
    • Spongy (Trabecular) bone - light framework of bone filaments (internal)
  • Trabeculae arranged along lines of stress
  • Macroscopic (gross) appearance of bones vary from one to the next
    • Influenced by:
      • Genetics - role of DNA etc.
      • Metabolism and nutrition
      • Function and mechanical stress
  • All bones will have:
    • Articular surfaces - usually smooth and at ends of bone to form joints
    • Identifiable prominences - ridges, crests, tubercles and tuberosity - points of attachment for ligaments, muscles, tendons etc.

Anatomical Classification

  • According to gross shape:
    • Long bones - diaphysis (shaft) and epiphysis (expanded ends)
    • Short bones - small, regular shape (e.g. carpus and tarsus)
    • Irregular bones - many exaggerated prominences (e.g. vertebrae)
    • Flat bones - thin and curved around body (e.g. scapula, skull, ribs)
    • Sesamoid bones - small and regular shaped - situated in tendons or ligaments at sites of stress

Functions of Bone

  • Protection - body organs (e.g. skull, ribs)
  • Support - suspension and attachment of soft tissue structures (e.g. muscles, ligament, thoracic structures)
  • Permit Movement - joint formation and muscle attachment
  • Blood Formation - marrow cavities of long bones
  • Storage - fat and can act as reserves of Ca when needed
  • Bone is a living tissue & requires a blood supply via the Nutrient Artery
  • and a nerve supply - small sensory supply for pain (mostly in periosteum) 

Introduction to Arthrology

  • Joints are formed when 2 or more bones come together 
  • Role of joints is to allow movement (to varying degrees)
  • The design of a joint will relate to its function

Primary Classification

  • Joints are primarily classified according to tissue filling joint space:
    • Fibrous
    • Cartilaginous
    • Synovial
  • Each class has its sub classifications

Secondary Classification - Fibrous Joints

  • Suture - Joint surfaces are serrated and close fitting (e.g. cranial sutures united by layer of fibrous tissue)
    • Role is developmental and allow deformation of head during birth - usually disappear in 3rd or 4th decades
  • Gomphosis - Peg & socket arrangement - fibrous ligament holds peg in socket e.g. teeth
  • Syndesmosis - plane joint surfaces united by inter-osseous ligament e.g. inferior tibio-fibular joint

Secondary Classification - Cartilaginous

  • Pad of Cartilage interposed between bone segments

  • Primary Cartilaginous (Synchondrosis)

    • Role is for longitudinal growth of bones
    • Hyaline cartilage between bone ends
    • No appreciable movement (e.g. Epiphyseal plates)
  • Secondary Cartilagenous (Symphysis)
    • Lie in midline of body
    • Bone ends covered in hyaline cartilage, fibrocartilage pad interposed between joint surfaces
    • Reinforced by ligaments, permit motion but very stable

Secondary Classification – Synovial Joints

  • Majority of body joints are synovial
  • Extremely mobile - motion limited by tension in overlying structures or apposition of anatomical structure
  • Chief Characteristics
    • Articular surfaces covered in Hyaline Cartilage for weight bearing and reduce friction between bones
    • Fibrous Capsule attached to or just beyond articular margins
    • Synovial Membrane attached to articular margins, lines capsule and covers any intra-articular bone. Highly vascular
    • Joint Cavity
    • Ligaments provide stability - may be thickenings in capsule or separate from capsule
    • Bursae - occasional synovial pouches form outside the boundaries of the capsules - reduce friction or pressure
  • Synovial Fluid is secreted by the Synovial Membrane - nutritional and lubricant
  • Occasional intra-articular fibrocartilage Disc or Meniscus - role is to increase congruency and dissipate weight


  • Role of synovial joints is to permit movement. Normal joint motion may occur:
    • Actively - due to muscle contraction
    • Passively - due to external forces (e.g. PT, gravity etc)
  • Movements possible at a joint:
    • Physiological - movements which can be produced actively (e.g. flexion / extension)
    • Accessory - movements which cannot be produced in isolation by primary muscle action (e.g. AP / PA glides, distraction)
  • Note: Accessory motion may occur during and are essential for a physiological motion 
  • Close Packed vs Loose Packed position - position of greatest Stability vs Instability 

Secondary Classification - Synovial Joints

  • Synovial Joints are subclassified according to the shape of Articular Surfaces:
    • Ball & Socket - permit multiaxial motion - e.g. hip, shoulder
    • Condyloid - modified B & S joint -
    • Permit active motion about 2 axes…
      • Passive motion may occur about 3rd axis - e.g. MCP joints 
    • Ellipsoid - another form of B & S joint - biconcave component is elliptical in shape
      • Active motion about 2 axes - e.g. wrist (radiocarpal) joint 
    • Hinge - permit uniaxial motion
      • Often associated with good articular fit and strong collateral ligaments - e.g. elbow joint
    • Pivot - permit rotation about long axis of bone
      • Associated with bone moving within osseo-fibrous ring - e.g. superior radio-ulnar joint
    • Plane - joint surfaces are flat (or close to it)
      • Permit gliding or twisting motion - e.g. Acromio-Clavicular joint
    • Saddle - reciprocally CONCAVO-CONVEX articular surfaces
      • Permit active biaxial motion - e.g. 1st carpo-metacarpal joint

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