Septic Arthritis vs Osteomyelitis

Question 1

define septic arthritis

Answer 1

infection of the synovial fluid within the joint

Question 2

define osteomylitis

Answer 2

infection of the fatty tissue and bone marrow within the bone

Question 3

what two joints are commonly impacted in septic arthritis? what about osteomylitis?

Answer 3

SA - knee (adults) and hip (children)

OM - vertebral column and long bones

Question 4

most common bacterias involved in septic arthritis?

Answer 4

staph aureus
group A strep
Neisseria gonorrhoeae

Question 5

most common bacterias involved in osteomyelitis?

Answer 5

staph aureus
salmonella in sickle cell pts

Question 6

common mechanisms of infection to get septic arthritis and osteomyelitis

Answer 6

hematogenous (most common): gonococcal infection, salmonella, pseudomonas
contiguous spread: septic bursitis
direct penetration: cellulitis, injection, abrasions, tattoos

Question 7

RF got septic arthritis and osteomyelitis

Answer 7

• extremes of age
• immunocompromised
• recent hospitalizations and procedures
• prev osteomyelitis or current ostemyelitis or SA for each other
• sickle cell disease
• chronic disease: DM, joint disease, chronic skin infection
• recent STI or infection
• IV drug use

Question 8

how does septic arthritis present compared to osteomyelitis?

Answer 8

acute monoarthritis

SA - more acute and emergent; there is still urgency in the case of osteomyelitis

both - red, hot, inflammed joint, may have decreased ROM/function, and fever
- SA is more likely to have swelling vs osteomyelitis

location of joint is also important to note + pt history

Question 9

how would you work up a potential septic arthritis and osteomylitis?

Answer 9

bloodwork
- CBC with diff
- lytes, cr, urea
- crp and esr
- blood culture x2
- bloodwork for comorbidities: A1c, liver enzymes
- STI testing: swabs for gonorrhea NAAT

imaging
- U/S or XR esp for a swollen joint
- MRI will have enough detail to allow you to differentiate SA vs osteomyelitis

procedures
arthrocentesis for synovial fluid analysis (SA)
- cell count, culture and sensitivity, crystals, gram stain
consider bone biopsy for osteomylitis if going for surgery for histopathological dx and id of causative organism if cannot do via blood culture

Question 10

how to tx septic arthritis?

Answer 10

therapeutic arthrocentesis to completely drain the joint - involve ortho

abx - IV vanco + ceftriaxone for 2 weeks then transition to PO if possible

adjust abx as cultures are returned

pt education: RTED intructions, red flags to return (hot swollen, fever), pain management (NSAIDs)

consider PT afterwards to help return to baseline

Question 11

how to tx osteomyelitis?

Answer 11

consult ortho - may need OR to remove infected bone

abx - IV vanco and ceftriaxone – adjust as cultures return

long course abx

PT afterwards to rehab