Septic Arthritis

Question 1

What is septic arthritis + what is the most common joint

Answer 1

• Infection –> inflammation in native/prosthetic joint(s)
• Acute or chronic
• Knee most common (50%)

Question 2

What causes it

Answer 2

• STAPH AUREUS most common

- Gonococcal arthritis = 2.8 cases per 100,000 person years

Question 3

What are some risk factors

Answer 3

• Age
• DM
• Prior joint damage e.g. rheumatoid gout, connective tissue disorder
• Joint surgery
• Hip or knee replacement
• Skin infection in combo
• Immunodeficiency

Question 4

What are the symptoms

Answer 4

• Single swollen joint - pain on passive/active movement
• Present at polyarticular arthritis
• Fevers + rigors
• Chest wall pain - if sternoclavicular, acromioclavicular, manubrosternal, sternocostal
• Buttock, hip, ant thigh pain = sacroiliac joint

Question 5

What are the signs

Answer 5

• bacteriaemia –> may cause prostration, vomiting, hypotension
• Swollen, warm, tender + painful on movement
• Effusion may be obvious

Question 6

What are some DDx

Answer 6

• Rheumatological disorders
• vasculitis
• Gout + pseudogout
• Drug-induced/ reactive/ viral arthritis

Question 7

What investigations would you perform

Answer 7

• BLOODS - inflammatory markers raised
• Synovial fluid aspirated + sent for culture + gram staining
• need at least 2 cultures to exclude bacteriaemia

IMAGING

• Plain radiographs - limited value - in late stage may show diffuse joint space narrowing –> cartilage destruction
• USS –> extra-/intra-atricular abnorm
• CT/MRI - Dx peri-articular abscess, joint effusion osteomyelitis (infection bone)
• Radionuclide scans - leukocyte scans localise areas of inflammation

Question 8

What is the treatment for septic arthritis

Answer 8

• Abx for S aureus + strep given IV 2-3weeks then switched to oral for 2-4weeks
• FLUCLOXACILLIN (clindamycin if allergic)
• If MRSA - vancomycin
• If gonococcal - CEFOTAXIME