Generally, a more indolent infection than a cellulitis or arthritis

May be difficult to differentiate from cellulitis


Classification by host (patient)

Class A: normal host

  • Systemic functions are normal
  • Much better prognosis

Class B: impaired host

  • Patient is immunocompromised, either locally, systemically or both
  • Local risk factors:
    • Peripheral vascular disease
    • Venous stasis
    • Lymphoedema
  • Systemic risk factors:
    • Smoking
    • Hypoxaemia
    • Chronic renal failure
    • Malignancy
    • Diabetes
    • Immunosuppressive drugs e.g. steroids
  • Must address any reversible/treatable factors

Class C: health of host does not allow full treatment

  • Treatment poses a greater risk than the infection itself
  • Surgery may not be possible due to the patient’s condition

Classification by disease (extent of bone involved)

Type 1: medullary osteomyelitis

  • Limited to the medullary cavity
  • Often caused by a solitary organism

Type 2: superficial osteomyelitis

  • Involvement of the cortex
  • Normally caused by an adjacent soft tissue infection

Type 3: localised osteomyelitis

  • Might involvement both the medulla and the cortex of the bone but does not involve its entire diameter

Type 4: diffuse osteomyelitis

  • Extensive infection
  • May occur on both sides of a joint or non-union
  • Involvement of the entire thickness of bone
  • Loss of stability



Often a history of previous open fracture/wound/surgery

Main complaint is normally localised pain

Pain is usually:

  • Chronic
  • Worsening
  • Aching
  • Not related to activity
  • Worse at night

Systemic features that can occur include:

  • Malaise
  • Sweat
  • Rigors
  • Anorexia


Look for any signs of tenderness or signs of infection

Skin can look normal if infection is deep


Full blood tests:

  • FBC
  • CRP
  • ESR
  • Blood culture

Wound swab

Xrays of the affected area

CT/MRI – not routinely done in A&E but may be done on follow up


Do not start antibiotics unless the patient is unwell

Treatment should wait until the causative organism is identified

The affected joint must be aspirated and the culture done of the aspirate

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