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Year 3 > Septic arthritis (MSK) > Flashcards

Septic arthritis (MSK) Flashcards

1
Q

What is septic arthritis.

A

The infection of 1 or more joints caused by pathogenic inoculation of microbes

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2
Q

What are the two routes of spread for septic arthritis?

A
  • direct inoculation - iatrogenic from arthrocentesis or trauma leading to open wounds around joints
  • haematogenous spread - spread from a distant site e.g. abscess, wound infection, septicaemia
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3
Q

What is the most common causative organism of septic arthritis in adults and children >2 years?

A

Staphylococcus aureus (gram +ve)

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4
Q

What is the most common causative organism of septic arthritis in young adults who are sexually active?

A

Neisseria gonorrhoeae (gram -ve diplococci)

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5
Q

What is the most common causative organism of septic arthritis in children <4 years?

A

Streptococcus pneumoniae

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6
Q

What is the most common causative organism of septic arthritis in a prosthetic joint?

A

Staphylococcus epidermis

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7
Q

Describe the mechanism of septic arthritis. (Low yield)

A
  • pathogen enters joint via bloodstream from nearby infection, or directly (e.g. via open fracture)/skin surface during trauma
  • infection of joint –> endotoxin production –> damage of articular cartilage –> cytokine release –> neutrophil attraction –> inflammation + damage
  • inflammatory response –> increase in intra-articular pressure –> compresses BVs supplying joint –> necrosis + joint destruction
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8
Q

What are the two types of septic arthritis?

A
  • non-gonococcal arthritis - majority, includes all other pathogens mainly S. aureus –> often a single joint affected (knee)
  • gonococcal arthritis - caused by N. gonorrhoeae, usually affects sexually active adolescents, spreads from infection of cervix, urethra or pharynx –> affects multiple joints and causes multiple skin lesions + tenosynovitis
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9
Q

What are the clinical features of septic arthritis? (4)

A
  • red, hot, swollen, painful, restricted joint
  • acute presentation (symptoms <2 weeks)
  • fever
  • usually single joint - most commonly knee joint (followed by hip, wrist, shoulder, ankle)
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10
Q

When can multiple joints (polyarthritis) be affected in septic arthritis? (2)

A
  • immunosuppressed
  • gonococcal arthritis
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11
Q

What is the triad of clinical features in septic arthritis?

A
  • fever
  • joint pain
  • restricted ROM
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12
Q

What might you see on examination of septic arthritis? (6)

A
  • red, hot, swollen, painful
  • immobile
  • severe pain on passive movement
  • pyrexic
  • signs for aetiology - trauma, injury, recent infection
  • erythema migrans
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13
Q

What are some risk factors for septic arthritis? (6)

A
  • underlying joint disease (OA/RA)
  • prosthetic joint
  • age>80
  • immunosuppression
  • diabetes
  • IV drug use
  • (HIV)
  • (exposure to ticks –> Lyme disease)
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14
Q

What is the 1st line investigation for septic arthritis?

A
  • urgent joint aspiration & culture
  • aspirate will be grossly purulent
  • send synovial fluid for MC&S, gram staining, WCC
  • rule out crystal arthritis
  • PCR if viral cause
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15
Q

What is arthrocentesis?

A

Joint aspiration - procedure in which synovial fluid is aspirated from a joint using a sterile needle (done before prescribing Abx)

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16
Q

What does synovial fluid analysis show in septic arthritis? (3)

A
  • appearance often yellow-green and turbid
  • increased WCC (>90% neutrophils)
  • gram stain: S. aureus –> gram +ve diplococci, coagulase +ve
17
Q

What other investigations can be done for septic arthritis? (7)

A
  • FBC - high WCC & neutrophils
  • CRP & ESR - high
  • blood cultures
  • viral serology
  • LFTs - may affect Abx choice, end-organ damage
  • MRI - osteomyelitis, oedema around synovium, spread of infection outside joint
  • plain joint radiographs - may appear normal, increased fluid in synovial part of joint, narrowing of joint space, destruction of bone adjacent to cartilage
18
Q

What are some differential diagnoses for septic arthritis?

A
  • osteoarthritis
  • psoriatic arthritis
  • rheumatoid arthritis
  • gout - synovial fluid polarising microscopy reveals urate crystals
  • pseudogout - pyrophosphate
  • haemarthrosis - blood
  • trauma
  • bursitis
  • cellulitis
  • TB - positive mycobacterial smears/cultures
  • Lyme disease - Lyme titre +ve
  • transient synovitis - normal aspirate
19
Q

What is the diagnostic criteria for septic arthritis based on?

A

Joint aspirate:

  • positive for bacteria/virus
  • high WCC
  • purulent aspirate
20
Q

What is the most important aspect of septic arthritis treatment?

A

Antibiotics + joint washout (therapeutic arthrocentesis)

21
Q

How do we manage emergency septic arthritis?

A
  • temporary joint immobilisation - use a splint
  • analgesia
  • immediate joint aspiration –> empirical antibiotic therapy
    • aspiration also provides symptomatic relief
    • empirical Abx initially, then tailor to patient demographics and clinical factors, narrow choice after MC&S
  • high dose IV Abx for 2 weeks –> switch to oral for up to 4 weeks
    • commonly flucloxacillin/clindamycin –> cefuroxime/gentamicin, cefuroxime+vancomycin
22
Q

What IV Abx is used in septic arthritis that covers gram +ve cocci?

A

Flucloxacillin

23
Q

What IV Abx is used in septic arthritis if patient is penicillin allergic?

A

Clindamycin

24
Q

How long should the Abx course be given for in septic arthritis?

A
  • 4-6 weeks
  • high dose IV Abx for 2 weeks –> up to 4 weeks oral Abx
25
Q

What is an empirical Abx agent used in septic arthritis?

A

IV vancomycin

26
Q

What Abx can be used in septic arthritis with sickle cell anaemia?

A

IV ceftriaxone

27
Q

How do we manage septic arthritis in a prosthetic joint?

A

Do not aspirate - refer to orthopaedic surgeon and aspirate in theatre

28
Q

How do we manage septic arthritis with systemic involvement?

A

Follow local protocol for suspected sepsis

29
Q

How is viral septic arthritis managed?

A

Typically self-limiting, no antiviral required

30
Q

When is physiotherapy done for septic arthritis?

A

As early as possible

31
Q

What are some complications of septic arthritis? (4)

A
  • antibiotic-associated allergic reaction
  • osteomyelitis
  • joint destruction
  • septicaemia
32
Q

Describe the prognosis of septic arthritis.

A

Delayed treatment can lead to irreversible joint destruction and subsequent disability

Year 3 (145 decks)

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