Updated: 12/22/2021

Septic Arthritis

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  • Snapshot
    • A 52-year-old man presents to his emergency department for worsening knee pain. He reports that his symptoms began approximately 10 days ago and is unable to bear weight on the affected knee. Medical history is significant for poorly controlled type II diabetes mellitus. On physical exam, the right knee is erythematous, swollen, and tender to palpation. There is decreased range of motion on the affected joint. Laboratory testing demonstrates an elevated erythrocyte sedimentation rate and C-reactive protein. An athrocentesis is obtained and demonstrates a white blood cell count of 65,000 cells/μL and gram-positive organisms.
  • Introduction
    • Clinical definition
      • infection of a joint leading to arthritis that can be caused by
        • bacteria
        • fungi
        • mycobacteria
  • Epidemiology
    • Risk factors
      • increasing age
      • diabetes mellitus
      • rheumatoid arthritis
      • prosthetic joints
      • intravenous drug abuse
      • skin infection
      • alcohol use
      • sexual activity
  • Etiology
    • Staphylococcus aureus
      • most common cause
    • Streptococci
      • second most common cause of nongonococcal arthritis
    • Neisseria gonorrhoeae
      • suspect in healthy and sexually active patient
    • Pseudomonas aeruginosa
      • typically seen in healthcare-associated infections
    • Borrelia burgdorferi
      • typically seen in patients in endemic areas
    • Mycobacterium tuberculosis
    • Staphylococcus epidermidis
      • typically seen in prosthetic joint infections
    • Pathogenesis
      • infectious agent can be spread to the joint by
        • hematogenously
        • direct inoculation
        • contiguously from the adjacent skin (e.g., cellulitis and cutaneous ulcers)
      • once the infectious agent arrives to the synovial membrane an inflammatory response ensues
  • Presentation
    • Symptoms
      • fevers may be present
      • joint pain
    • Physical exam
      • in most cases 1 joint is affected
        • a joint that is
          • warm
          • erythematous
          • swollen
          • restricted to movement
  • Imaging
    • Radiography
      • indication
        • can be used to get a baseline assessment of joint damage
  • Studies
    • Labs
      • ↑ erythrocyte sedimentation rate and C-reactive protein
    • Arthrocentesis
      • the best initial test for the evaluation for septic arthritis
    • Synovial fluid culture
      • the most accurate test and must be performed before antibiotic administration
      • findings
        • fluid is usually purulent
        • Gram stain may be positive
          • 30-50% sensitive
        • white blood cell count > 50,000 cells/μL
  • Differential
    • Gout
    • Pseudogout
    • Inflammatory arthritis (e.g., rheumatoid arthritis)
    • Viral arthritis (e.g., hepatitis B and C and parvovirus B19)
  • Treatment
    • Medical
      • intravenous empiric antibiotics
        • indication
          • treatment of choice after athrocentesis is performed to target the most likely organism
            • best if a minimum of 2 blood cultures are performed prior to administering antibiotics
            • antibiotics then becomes tailored to the specific organism when susceptibility results return
        • drugs
          • vancomycin + a third-generation cephalosporin
            • an initial empiric treatment option for septic arthritis
          • vancomycin
            • used when
              • Gram stain of synovial fluid shows gram-positive cocci
          • third-generation cephalosporin
            • used when
              • Gram stain of synovial fluid shows gram-negative bacilli
    • Operative
      • joint drainage
        • indication
          • used along with antibiotics to treat septic arthritis
            • septic arthritis represents a closed abscess
        • modalities
          • needle aspiration
          • arthroscopic drainage
          • arthrotomy
  • Complications
    • Osteomyelitis
    • Sepsis
  • Prognosis
    • Dependent on a number of comorbid conditions (e.g., age and immunosuppresion)
      • ranges 10-15%
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(M2.OR.17.4817) A 47-year-old woman presents to the emergency department with pain in her right knee. She states that the pain started last night and rapidly worsened, prompting her presentation for care. The patient has a past medical history of rheumatoid arthritis and osteoarthritis. Her current medications include corticosteroids, infliximab, ibuprofen, and aspirin. The patient denies any recent trauma to the joint. Her temperature is 99.5°F (37.5°C), pulse is 112/min, blood pressure is 100/70 mmHg, respirations are 18/min, and oxygen saturation is 98% on room air. On physical exam, you note erythema and edema of the right knee. There is limited range of motion due to pain of the right knee.

Which of the following is the best initial step in management?

QID: 109405

CT scan

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(1/66)

Broad spectrum antibiotics

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(2/66)

Aspiration

91%

(60/66)

Surgical drainage

2%

(1/66)

Conservative therapy

3%

(2/66)

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(M2.OR.17.4760) A 3-year-old patient is brought to the emergency department by her mother due to inability to walk. The child has been limping recently and as of this morning, has refused to walk. Any attempts to make the child walk or bear weight result in crying. She was recently treated for impetigo and currently takes a vitamin D supplement. Physical exam is remarkable for an anxious appearing toddler with knee swelling, erythema, and limited range of motion due to pain. Her mother denies any recent trauma to the child's affected knee. Temperature is 103°F (39.4°C), pulse is 132/min, blood pressure is 90/50 mmHg, respirations are 18/min, and oxygen saturation is 99% on room air. Which of the following is the best initial step in management?

QID: 109015

Radiograph

10%

(3/30)

MRI

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Ultrasound

3%

(1/30)

Broad spectrum antibiotics

7%

(2/30)

Synovial fluid analysis

77%

(23/30)

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(M2.OR.16.4686) A 55-year-old IV drug user comes into the emergency department after four days of pain in his right ankle. The patient is lethargic and unable to answer any questions about his medical history. His vitals are HR 110, T 101.5, RR 20, BP 100/60. His physical exam is notable for track marks in his toes and his right ankle is erythematous and swollen. Moving any part of the right foot creates a 10/10 pain. A radiograph revels no evidence of fractures. A Gram stain of the joint fluid aspirate demonstrates purple cocci in clusters. The fluid is yellow, opaque, with more than 70,000 cells/mm^3 (80% neutrophils). What is the most likely diagnosis?

QID: 107385

Monosodium urate crystal formation

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Salmonella infectious arthritis

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Staphylococcus infectious arthritis

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Borrelia infectious arthritis

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Osteoarthritis

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(M3.OR.15.30) A 42-year-old man with a history of gout and hypertension presents to his family physician with a complaint of increased left knee pain over the past 2 days. He also reports swelling and redness of the left knee and is unable to bear weight on that side. He denies any prior surgery or inciting trauma to the knee. His temperature is 97.0°F (36.1°C), blood pressure is 137/98 mm Hg, pulse is 80/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical examination reveals a left knee that is erythematous, swollen, warm-to-touch, and extremely tender to palpation and with attempted flexion/extension movement. His left knee range of motion is markedly reduced compared to the contralateral side. Joint aspiration of the left knee is performed with synovial fluid analysis showing turbid fluid with a leukocyte count of 95,000/mm^3, 88% neutrophils, and a low glucose. Gram stain of the synovial fluid is negative. Results from synovial fluid culture are pending. Which of the following is the best treatment regimen for this patient?

QID: 103321

Acetaminophen and ibuprofen

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(0/5)

Ceftriaxone

20%

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Indomethacin and colchicine

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(1/5)

Piperacillin-tazobactam

40%

(2/5)

Vancomycin and ceftazidime

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