Septic Arthritis Flashcards by Charlotte Tebbutt

What is septic arthritis?

an infection within a joint space

it can affect both native and prosthetic joints

it is typically acute, but can be chronic in some cases

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What are the risks associated with acute septic arthritis?

it can lead to sepsis and death (mortality of 10-20%)

prompt diagnosis and management are important to reduce risk of mortality and reduce long-term disability

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How do joints tend to become infected?

Who is more prone to a joint infection?

joints can be infected by direct injury or by bloodborne infection from an infected skin lesion or other site (bacteraemia)

chronically inflamed joints (e.g. in RA) are more prone to infection than normal joints

those who are at a higher risk of joint infection are:

infants
the elderly
immunosuppressed
those who abuse alcohol

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How does septic arthritis typically present?

typically presents as a single warm, red, painful joint with pain whenever the joint is moved

!!! any warm, red, painful joint should be considered septic arthritis until proven otherwise !!!

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What is the most common cause of septic arthritis?

Staphylococcus aureus

in adults, many cases are caused by gonorrhoea (especially in the elderly or immunosuppressed)

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What other organisms can cause septic arthritis?

streptococci
other species of staphylococcus
Neisseria gonorrhoeae
Haemophilus influenzae (in children)
^^ these and other Gram-negative organisms in the elderly or complicating RA

the cause is nearly always bacterial, but in rare cases can be viral or fungal

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What should be done immediately with any joint that is hot, red and tender?

What other symptoms are usually present?

any joint that is red, hot and tender is a septic joint until proven otherwise as septic arthritis can rapidly cause irreversible joint damage

these joints must be aspirated

patients often have systemic fever and raised inflammatory markers (CRP and ESR) too

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What is the risk of septic arthritis after joint replacement and joint revision procedures?

the risk is relatively high for joint replacement

about 2% risk for primary infection at the time of joint replacement procedure

risk can be as high as 20% for joint revision procedures

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What are the risk factors for septic arthritis?

diabetes mellitus
increasing age
previous joint damage - e.g. gout, rheumatoid arthritis
joint surgery
prosthetic joint
cellulitis - particularly if overlying a prosthetic joint
immunodeficieny
IV drug use
history of STIs

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What is the typical presentation of septic arthritis?

Which joints are most commonly affected?

a single red, hot, painful joint

polyarthritis is uncommon

it can affect any joint but most commonly affects the hip and knee

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How do children and adults tend to move when they have septic arthritis?

patients are typically unwilling to move the joint due to severe pain

children tend to limp and refuse to weight bear

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Which groups of patients presenting with septic arthritis does particular care need to be taken with?

in the elderly, immunosuppressed and patients with RA

the clinical picture of SA is less dramatic so a high index of suspicion is needed to avoid missing treatable but potentially severely destructive septic arthritis

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What will the joint be like on examination for septic arthritis?

the joint is usually held immobile by muscle spasm so will be exquisitely tender to move
effusion
erythema
swelling

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What other symptoms may a patient with septic arthritis have?

fever +/- rigors
if bacteraemia is present, there may be vomiting and hypotension

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What is different about septic arthritis caused by gonococcal disease?

this is often associated with multiple skin lesions

multiple joints are often affected (but not always)

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How does the presentation of septic arthritis of a prosthetic joint differ?

more likely to be a chronic, low-grade infection
pain gradually increases over weeks or months
often no fevers
often no joint swelling or redness

What are the differential diagnoses for septic arthritis in children?

transient synovitis
Perthes disease
slipped capital femoral epiphysis (SCFE)
viral arthritis
trauma
non-accidental injury

What is the main differential diagnosis in adults?

GOUT

this typically presents without fevers or signs of sepsis

the appearance and examination of gout and septic arthritis are incredibly similar

What are the other differential diagnoses for septic arthritis in adults?

rheumatoid arthritis
reactive arthritis
- this tends to affect multiple joints, in a symmetrical pattern
viral arthritis
- tends to affect multiple joints
Lyme disease
Infective endocarditis
- septic arthritis is a complication of IE

In general, what investigations are performed to diagnose septic arthritis?

diagnosis is typically on the basis of blood tests (raised ESR and CRP) and positive joint aspiration culture

there are many other supportive investigations which may detect septic arthritis where the first line investigations have failed

Which blood tests are used in the investigation of septic arthritis?

Full blood count

CRP and ESR are both typically raised

blood cultures are also often positive

leucocytosis (raised WCC) is usually seen unless the patient is severely immunosuppressed

What is the gold standard test for septic arthritis?

JOINT ASPIRATION FOR SYNOVIAL FLUID

fluid is often purulent
fluid is sent for urgent Gram staining and culture

What should not be given before joint aspirate is taken?

aspiration should be done **_BEFORE_** giving the patient **_antibiotics_** unless the patient is septic and acutely unwell

In what groups of patients should extra caution be taken when aspirating a joint?

any patients with a **_prosthetic joint_** aspiration should only be performed by a specialist there is a high risk of **causing septic arthritis** if it is not already present

What is an added benefit of aspirating a joint?

If there is a large effusion, aspiration of the joint can also provide an **analgesic effect**

What should be remembered when taking blood cultures?

need to take **_at least 2 samples_** from **_different sites_** samples need to be taken **_BEFORE_** giving the patient **_antibiotics_**, unless they are septic and acutely unwell

If gonococcal disease is suspected as the cause, what other tests are considered?

* consider swabs of rectum, throat, vagina or urine sample (men) for gonococcal PCR +/- culture

What other swabs may be taken and what might they show?

* skin wound swabs * sputum * throat swab * urine they may be positive and indicate the source of infection

What may X-rays show in septic arthritis?

they are often not useful - especially in the first few days of infection in chronic cases, they may show **_osteomyelitis_** they may show **_fat pad swelling_** as a sign of inflammation

What may ultrasound and CT/MRI show in septic arthritis?

**_Ultrasound:_** * may show joint effusion - this is a non-specific sign **CT and MRI:** * can see abscess and joint effusion

When is a radionuclide bone scan used and what may it show?

it is useful in **chronic cases** where the cause of joint pain is unclear it is **non-specific** and shows areas of **_high cell turnover_** this indicates an **inflammatory process**

When should treatment for septic arthritis be started?

treatment should be started **_immediately upon diagnosis_** as **joint destruction** occurs within days the joint should be **_immobilised initially_** and then **physiotherapy** started early to prevent **stiffness** and **muscle wasting**

In general, what is the treatment for septic arthritis and how long should it be given for?

usually involves a combination of **_surgical washout_** of the joint and **_IV antibiotics_** IV antibiotics are given for **1-2 weeks** it is usual to give 2 antibiotics to which the organism is sensitive for 6 weeks, then one for a further 6 weeks orally

What is the typical antibiotic that is given for septic arthritis? What if the patient is allergic to penicillin?

* **_FLUCLOXACILLIN IV_** - 2g every 6 hourly (QID) * + **_FUSIDIC ACID_** - 500mg every 8 hours orally * if penicillin allergy then give **_ERYTHROMYCIN IV_** - 1g every 6 hourly * or **_CLINDAMYCIN IV_** - 600mg every 8 hourly

What is the antibiotic treatment for an immunosuppressed patient with septic arthritis?

* **_FLUCLOXACILLIN IV_** - 2g every 6 hourly * also **_GENTAMICIN_** should be given to cover **Gram-negative organisms**

What antibiotics are given if streptococcus or gram-negative organisms are causing the septic arthritis?

* **_CEFTRIAXONE IV_** - 2g once daily

How is the joint immobilised initially when starting treatment for septic arthritis?

**_JOINT SPLINTING_** this is recommended for the first few days the knees are in extension, wrist in neutral or slight extension and elbow at 90 degrees once pain settles, early mobilisation promotes healing and reduces contractures

What is the treatment for infected prostheses?

* if chronically infected, the prosthesis is removed * the joint space is filled with an antibiotic impregnated spacer for 3 - 6 weeks * a new prosthesis is then inserted * the whole process is covered by antibiotics

What is the mortality risk of septic arthritis? What risk factors are associated with increased risk of death?

**10-20%** mortality **age \>65** and **shoulder, elbow or multiple joints** affected are associated with increased risk of death typically patients have **reduced function** of the affected joint for life