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This guideline covers the diagnosis and management of acute septic arthritis and acute haematogenous osteomyelitis in infants and children. It does not cover the following situations:

  • Chronic osteomyelitis
  • Osteomyelitis related to trauma, open fractures
  • Post-surgical osteomyelitis (metalware in situ)
  • Spinal infection

Clinical features

There is overlap in the way that osteomyelitis and septic arthritis can present. Both conditions should be suspected when a child presents with fever, reduced use of a joint or limb, and localised tenderness.

Causative organisms

Age group Common Less common Rare
0 - 3months Group B streptococcus
Staphylococcus aureus*
Enterobacteriaciae Streptococcus pyogenes
Streptococcus pneumoniae
Salmonella typhi
Haemophilus influenzae type b
Neisseria meningitidis
3 months - 5 years Staphylococcus aureus* Kingella kingae
Streptococcus pyogenes
Streptococcus pneumoniae
Salmonella typhi
Haemophilus influenzae type b
Neisseria meningitidis
≥5 years Staphylococcus aureus* Streptococcus pyogenes

*Staphylococcus aureus and MRSA. MRSA is estimated to account for ≤10% of invasive S. aureus isolates in Auckland children. Empiric treatment for MRSA is not usually recommended, although this may be appropriate in children who are known to be colonised with MRSA or are very unwell.

Pathogens to consider in special groups


Kingella kingae can cause septic arthritis in young children, often with an indolent presentation where the child does not appear particularly unwell.1 There may be only a low grade fever and only slightly elevated CRP. Kingella can cause spondylodiscitis and endocarditis, so careful examination of the spine and heart is needed.

Asplenic & immune compromised

Streptococcus pneumoniae, Haemophilus influenzae type b (Hib), Salmonella typhi


Group B streptococcus, Escherichia coli (Lumbar puncture required)


Haemophilus influenzae type b, Streptococcus pneumoniae

Clinical assessment

Carefully examine to look for signs of sepsis and the possibility of multi-focal infection, including detailed musculoskeletal, respiratory, abdominal, neurologic and cardiovascular assessments. The possibility of meningitis should always be considered in young infants. The Paediatric Registrar on call is able to assist with the acute management of unstable patients with suspected sepsis or multifocal infection, and neonates. Very high CRP and ESR should raise concern about possible multi-focal infection.2

Acute rheumatic fever should be considered in Maori and Pacific Island children, particularly those who present with mono-arthritis.3

Initial investigations

Blood tests

Always obtain blood cultures prior to starting antibiotics

Synovial fluid

Send fluid to the laboratory in a sterile pottle and also inoculate directly into a blood culture bottle, which can improve the identification of Kingella kingae. A leucocyte count of ≥50,000 cells/mm3, with a predominance of neutrophils, is strongly suggestive of bacterial infection.

Imaging investigations

Plain xrays are performed acutely. Further imaging (ultrasound, bone scan, MRI) may be organised at the discretion of the orthopaedic team.

Further investigations

Lumbar puncture

Young infants may require a lumbar puncture; this is essential if they have infection caused by Group B Streptococcus, Streptococcus pneumoniae or E. coli which are common causes of bacterial meningitis in young infants. Please discuss with Infectious Diseases / General Paediatrics.

Cardiology assessment and echocardiogram

Cardiology referral may be indicated if there persistent bacteraemia for several days, a new murmur, and/or underlying congenital heart disease. The yield from echocardiography in transient S. aureus bloodstream infection with a structurally normal heart is very low. Cases should be discussed with Infectious Diseases / Cardiology.

Initial antibiotic treatment for bone and joint infection

Age group Antibiotic
Infant < 3months Flucloxacillin + cefotaxime
3months - 36 months Flucloxacillin
if suspicion of Kingella kingae
Amoxicillin + Clavulanic acid OR cefazolin
>3 years Flucloxacillin

Please discuss with Paediatric Infectious Diseases if there is antibiotic allergy, suspicion of MRSA, or other special circumstances such as complicated/multifocal infection or underlying immune compromise.

Antibiotic doses

IV antibiotics

As a general principle, dosing should be as for severe infection - ie the maximum dose in the range.

Newborn infants: link to NWH drug doses

Older infants and children:

Flucloxacillin 50mg/kg/dose q 6hrly (max 2grams/dose)
Amoxicillin + Clavulanic acid 30mg/kg/combined dose q 6-8hrly (max 1.2grams combined, q-8hrly)
Cefazolin 50mg/kg q8hrly (max 2grams q8hrly)

Oral antibiotics (high doses are needed for treatment of bone and joint infection)

Cephalexin 25mg/kg/dose q 6hrly (max 1gram q6hrly)
Flucloxacillin 25mg/kg/dose q 6hrly (max 1gram q6hrly) (flucloxacillin suspension is unpleasant tasting. 250mg/5mls strength reduces the dose volume. Recommend test dose in hospital and if poor adherence suspected, choose an alternate agent)
Amoxicillin + Clavulanic acid 25mg/kg/dose q 8hrly (max 625mg combined, tds)

Ongoing treatment

Osteomyelitis is usually treated for 4 - 6 weeks4 and septic arthritis is usually treated for 2 - 3 weeks5. Complicated infections often require a longer course of antibiotics. Please discuss with the Infectious Disease team.

Antibiotics should be rationalised to the narrowest spectrum agent as soon as a pathogen is identified and susceptibilities are available.

Home IV antibiotics

May be appropriate in selected children ≥1yr of age, with no history of anaphylaxis, on no more than two antibiotics and with appropriate IV access. A detailed home IV nursing assessment must be completed to ensure the suitablility of the child, appropriate family circumstances and community nursing supports are available. Home IV suitability assessment packs and resources are located in the 24A CN office. Home Antibiotics are delivered via elastomeric infusor devices or bolus administration by a caregiver/parent with support from the homecare nursing service. Contact the ward 24A pharmacist for advice on how to organise antibiotics for discharge.

Intravenous to oral switch

Some patients may be able to change to oral antibiotics part-way through their treatment. This decision is made by the primary Orthopaedic consultant, based on clinical progress and sustained improvement in inflammatory markers. Important issues to consider include:

  • Disease factors including:
    • Pathogen: MRSA or other uncommon organism
    • Complexity: multiple surgical debridements, slow clinical response, slow improvement in CRP
  • The bone or joint involved: pelvic and flat bones often require longer treatment.
  • Patient factors including:
    • Age of patient
    • Ability to swallow medicine (either syrup or capsules)
    • Whether presentation to hospital was delayed
    • Immune compromised host
    • Poor oral absorption of medicines
    • Suspected poor adherence to oral antibiotics

If oral antibiotics are prescribed, it is important to ensure an appropriately high dose is prescribed at a frequency that will achieve equivalent tissue concentrations to IV therapy. It is also important to ensure oral medicine is tolerated by the patient and that caregivers can competently give the medicine. Monitoring of antibiotic levels may be required in some situations - please discuss with the Infectious Diseases team.

Discharge monitoring and potential complications

Once the acute phase has settled, children being treated for bone and joint infections should have weekly blood tests to monitor inflammatory markers, FBC and liver enzymes.

Prior to discharge, the Orthopaedic House Officer should communicate with the ward pharmacist and ensure that any prescription for antibiotics has been filled and that monitoring and support for adherence is in place. This may include measures such as a medication diary, regular outpatient clinic visits, homecare nurse visits and phone calls.

A clear plan should be in place for follow-up of laboratory results after discharge.

Re-admissions for complications come under the care of the Orthopaedic service.

Delayed beta lactam hypersensitivity may occur 3 - 4 weeks into treatment. This is most frequently seen in children treated with high dose flucloxacillin.6 Features include maculopapular rash, fever, neutropaenia and occasionally abnormal liver tests. Re-admission for supportive care and modification to the child's antibiotic treatment may be required. Please consult the Infectious Diseases service.

PICC line complications include blockage, infection and thrombosis. The child should be initially assessed by the homecare nurses or in CED (out of hours) and may need re-admission and line removal. Antibiotics may need to be modified.


  1. Peltola,H, Paakonnen, M. Bone and Joint Infections. Pediatr Clin N Am 2013; 60: 425 - 436.
  2. Street M, Puna R, Huang M, Crawford H. Paediatric Acute Haematogenous Osteomyelitis. J Pediatr Orthop 2015; 35: 634-639.
  3. Mistry RM, Lennon D, Boyle MJ, Chivers K, Frampton C, Nicholson R, Crawford H. Septic arthritis and acute rheumatic fever in children: the diagnostic value of serological inflammatory markers. J Pediatr Orthop. 2015; 35(3):318-22.
  4. Peltola H & Paakonnen M. Acute Osteomyelitis in Children. New England Journal of Medicine 2014; 370: 352 - 360.
  5. Peltola H, Paakkonen N, Kallio P, Markku J. T. Prospective, Randomized Trial of 10 Days versus 30 Days of Antimicrobial Treatment, Including a Short- Term Course of Parenteral Therapy, for Childhood Septic Arthritis. Clinical Infectious Diseases 2009; 48, 1201 - 10
  6. Van den Boom J, Kristiansen JB, Voss LM, Stott NS. Flucloxacillin associated neutropenia in children treated for bone and joint infections. J Paediatr Child Health.2005; 41(1-2):48-51.
  7. Dartnell J, Ramachandran M, Katchburian M. Haematogenous acute and subacute osteomyelitis: a systematic review of the literature. Journal of Bone and Joint Surgery (Br) 2012; 94(5): 584-95.
  8. Bradley J & Nelson JD. Nelson's Pocket Book of Pediatric Antimicrobial Therapy 2014 ed.

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Document Control

  • Date last published: 01 August 2016
  • Document type: Clinical Guideline
  • Services responsible: Paediatric Infectious Diseases, Paediatric Orthopaedics, ADHB Pharmacy
  • Author(s): Rachel Webb, Elizabeth Wilson, Emma Best, Lesley Voss, Susan Stott, Hamish Crawford, Eamon Duffy, Preetika Vareed, Sue Whaitiri, Kelly Olliff
  • Owner: Rachel Webb
  • Editor: Greg Williams
  • Review frequency: 2 years

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