05/03/2021 [septic arthritis, hand/foot bones, CRMO, lupus]]

Question 1

Most common causative organism for septic arthritis

Answer 1

Stephylococcus aureus [mainly meticillin-sensitive strains]

Question 2

Other less common cause of septic arthritis. Which population is this common in?

Answer 2

Gonococcal arthritis in 2.8 per 100k persons .

Becoming increasingly more common in elderly and the immunosuppressed.

Question 3

RF for septic arthritis

Answer 3

Increasing age, DM, prior joint damage, joint surgery, skin infection, immunodeficiency

Question 4

Presentation of septic arthrits

Answer 4

Single swollen joint with pain on active or passive movement.
May present as polyarticular arthritis in a minority of patients.
Fever and rigors present in majority of cases.

Question 5

What is a common concerning finding in septic arthritis and how could this present?

Answer 5

Bacteraemia. May cause prostation, vomiting or hypotension.

Question 6

How may infection of sacroiliac joint present in septic arthritis?

Answer 6

Buttock, hip or anterior thigh pain

Question 7

Why may septic arthritis be missed in children?

Answer 7

Localising signs may be absent, and may be confused with more common conditions like transient synovitis/trauma.

Question 8

Presentation in children [incl. age group]

Answer 8

Most commonly preschool infants/toddlers.
Hip and knee represent a third of cases each, with other joints making up the remainder.
Pts usually present with fever, joint pain and/or unwillingness to move the affected joint.

Question 9

Which joints most commonly involved?

Answer 9

Knee [about half of cases], followed by hip, shoulder, ankle and wrists.

Question 10

DDx for septic arthritis

Answer 10

Primary rheumatological disorders, vasculitis, gout, pseudogout. 
Drug-induced arthritis [like steroids].
Reative arthritis.
Lyme disease.
Viral arthritis. 
infective endocarditis.