Reactive and Infective (septic) arthritis

Question 1

What is reactive arthritis?

Answer 1

An inflammatory arthritis that occurs following exposure to certain gastrointestinal and
genitourinary infections

Question 2

What bugs cause reactive arthritis?

Answer 2

Common preceding infections in childhood are enteric bacteria including Salmonella, Shigella, Campylobacteria, Yersinia

Question 3

What are the less common causes of reactive arthritis?

Answer 3

▪ Viral infections
▪ STIs in adolescents: chlamydia, gonococcus
▪ Mycoplasma
▪ Borrelia burgdorferi (Lyme disease)
▪ Rheumatic fever and post-streptococcal reactive arthritis, particularly in
developing countries

Question 4

Why is reactive arthritis important?

Answer 4

• Most common form of arthritis in childhood

* Characterised by transient joint swelling (usually < 6 weeks) often of the ankles or knees

Question 5

What are the clinical features of reactive arthritis?

Answer 5

• History of gastrointestinal or genitourinary infection 1-4 weeks before onset of arthritis
• Transient joint swelling of ankles or knees usually
• Low grade fever

Question 6

What are the investigations you would do for reactive arthritis?

Answer 6

• ESR/CRP: mildly elevated
• Urogenital/stool culture
• X-ray: normal

Question 7

What is the management of reactive arthritis?

Answer 7

• NSAIDs for pain relief
o Others: steroids, DMARDs
• Self-resolving

Question 8

What is septic arthritis?

Answer 8

• Infection of one or more joints due to pathogenic inoculation of microbes
o Usually due to haematogenous seeding from a distant infection
o Less commonly, can occur due local extension of local sepsis, iatrogenic implantation
or post-trauma
o In children, it may result from adjacent osteomyelitis into joints where the capsule
inserts below the epiphyseal growth plate

Question 9

Who gets septic arthritis?

Answer 9

Most common in children < 2 years old

Question 10

What pathogens cause septic arthritis?

Answer 10

Most common site: hip (75%)

o STAPHYLOCOCCUS AUREUS = most common
o < 3 months: STAPH AUREUS, Group B Strep
o 3 months – 5 years: Kingella kingae, STAPH AUREUS, beta-haemolytic
streptococci, Strep pneumoniae, meningococcus (rarely Hib)
o > 5 years: Staph aureus, beta-haemolytic Streptococci
o Sickle cell disease: S aureus is still most common but salmonella also associated with
SCD
o Neisseria gonorrhoea: adolescents

Question 11

What are the RFs for septic arthritis?

Answer 11

Underlying illness e.g. immunodeficiency, sickle cell disease

Question 12

What are the clinical features of septic arthritis?

Answer 12

• PAINFUL, HOT, SWOLLEN, RESTRICTED JOINT
• Acutely unwell, febrile child
• Infants may hold the limb still (pseudoparesis, pseudoparalysis)
• Infants will cry when the affected limb is moved
• Joint effusion may be visible in peripheral joints
• Co-existent osteomyelitis (15%)
• Pain may be referred to the knee
• May present with limp initially
• Often diagnosed late due to poor localisation of symptoms and normal plain X-ray findings

Question 13

What investigations do you do for septic arthritis?

Answer 13

• WCC
• Raised acute-phase proteins: CRP, ESR
• Blood cultures
• Ultrasound of deep joints (reveal an effusion)
• X-rays to exclude trauma
o Changes not usually seen until 2-3 weeks after
o May show widening of joint space, soft tissue
swelling and ill-defined articular margins
• Aspiration under ultrasound guidance is
the definitive investigation
o This should be performed IMMEDIATELY
o Synovial fluid Gram stain and culture
o Synovial fluid WCC
• MRI
o Done if high index of suspicion

Question 14

What is the kocher criteria for septic arthritis?

Answer 14

Kocher Criteria for Septic Arthritis:
distinguishes septic arthritis from
transient synovitis in a child with an
inflamed hip
Ÿ Non weight-bearing
Ÿ Temperature > 38
Ÿ ESR > 40mm/h
Ÿ WBC > 12,000 cells/uL
Ÿ A point for each criteria
Ÿ Higher points = septic arthritis
more likely

Question 15

What is the management of Septic arthritis?

Answer 15

o Prolonged course of antibiotics (initially IV for 2 weeks, followed by 4 weeks of oral
antibiotics)
▪ Suspected Gram-positive
• Vancomycin + joint aspiration
• 2nd line = clindamycin or cephalosporin + joint aspiration
▪ Suspected Gram-negative
• 3rd generation cephalosporin (e.g. ceftriaxone) + joint aspiration
• 2nd line = IV ciprofloxacin + joint aspiration
o Affected joints should be aspirated to dryness as often as required (through closed
needle aspiration or arthroscopically)
o Washing out of the joint or surgical drainage may be required
o Joint is initially immobilised in a functional position but must subsequently be
mobilised to prevent permanent deformity