Septic arthritis

Question 1

What may the results of blood tests show in joint infection?

Answer 1

raised WCC and neutrophilia
raised CRP and possibly raised ESR (though ESR takes longer to rise)
may show bacteraemia on culture

Question 2

How long does it take for an XR to show changes in osteomyelitis or joint infection?

Answer 2

2 weeks

Question 3

what is the only way to make the diagnosis confidently in joint infection - ie what is the gold standard diagnostic test?

Answer 3

joint aspiration

Question 4

what is the main way that native joints become infected?

Answer 4

bacteraemia ie haematological seeding

Question 5

what other test needs to be done alongside joint aspiration?

Answer 5

blood cultures

Question 6

what are we looking for in a joint aspirate?

Answer 6

pus - is it thick, cloudy, containing many leukocytes? then send to the lab for culture

Question 7

How is septic arthritis managed in sb who is on RA medications?

Answer 7

remove any pus from the joint eg by joint aspiration and washout
stop immunosuppression drugs
double prednisolone dose
give analgesia
rest/splinting/crutches to off-load joint
give a prolonged dose of antibiotics - 6 WEEKS, IV initially and then orally

Question 8

why is the steroid dose doubled in infection or surgery if sb is taking steroids regularly?

Answer 8

if sb is taking steroids regularly, the adrenal response is blunted so the body needs help to produce more steroid hormones in time of stress

Question 9

at what level of CRP would you be suspicious of infection if a pt has co-existent RA?

Answer 9

CRP >100

Question 10

what are the risk factors for septic arthritis?

Answer 10

RA
DM
prsotehtic joints 
pts on long term steroids 
>65 yrs old 
any cause for bacteraemia 
direct/penetrating trauma 
local skin breaks/ ulcers 
damaged joint 
immunosuppression

Question 11

What is the most common and second most common causative organism for septic arthritis in NATIVE joints in both children and adults?

Answer 11

S. aureus - most common

Strep is the second most common

Question 12

What are the causative organisms for native joint infection?

Answer 12

S. aureus
Streptococci
Neisseria gonorrhoea
G- baccili eg E. coli nd Pseudomonas aeruginosa
anaerobes - eg Clostridium and Bacteroides (G- rod)
Mycobacterium
Fungi

Question 13

In which types of pts does mycobacteria and fungi cause native joint infection?

Answer 13

the immunocompromised

Question 14

In which types of pts would you expect to see G- bacilli causing joint infection?

Answer 14

extremes of age
systemically unwell
IVDU
UTI

Question 15

In which pts would you expect to see N. gonorrhoea as the cause of septic arthritis?

Answer 15

young, sexually active
MSM
20-40 yr olds

Question 16

Why is H. influenzae no longer the main causative organism for septic arthritis in children?

Answer 16

vaccination

Question 17

What is different about presentation of gonococcal arthritis from normal septic arthritis?

Answer 17

1. it is typically a POLYARTHRITIS an not a monoarthritis like septic arthritis usually is
2. it is not just an arthritis but a TENOSYNOVITIS as well
3. presents with a maculopapular - pustular rash in the palms and soles that is painful before visible. grey in the centre with surrounding necrosis and erythema

Question 18

How would you investigate a gonococcal arthritis?

Answer 18

mucosal swab and blood cultures

you would NOT do a joint aspiration or synovial biopsy

Question 19

What is the typical presentation of a septic joint?

Answer 19

inflammatory pillars - red, swollen, hot joint
fever may be present
90% are monoarthritis
knee > hip > shoulder