Septic arthritis

Septic arthritis - acutely inflammed joint and may destroy within 24hrs. Treat empirically with antibiotics.

Signs/symptoms

• Swollen, red joint
• associated fevers, chills and rigors, consider localised symptoms.

DDX - OA, gout, haemarthrosis, less likely psoriatic arthritis, reactive arthritis.

Ix-

1. Imaging - x-rays may be normal, consider CT, U/S, MRI.
2. FBE, ESR, CRP - raised WCC, inflammation.
3. U&E and LFT for baseline.
4. Joint aspiriate - appearance: turbid,yellow, low viscosity, microscopy: raised WCC, neutrophils. Culture& sensitivty: for the organism + sensitivity. also for polarized light microscopy: crystals (negatively bifringement crystals for gout)

Mx-

1. Analgesia
2. Empirical antibiotics until culture is known. Flucloxacillin (as most common organism is SA. consider benzylpenicillin + gentamicin)
3. Consult microbiologist
4. Consider joint wash-out especially in prosthetic knee.
5. Seek/ treat underlying cause - immunosupression? focus of infection?

Other medication to consider

1. MSSA - 1st/2nd gen cephalosporin - cephazolin/cephalexin.
2. Gp D streptococci - (like GP A but affects immunocompromised patients). Ideal medication would be penicillin as you would prefer a narrow spectrum medication to avoid antibiotic resistance (unnecessay killing of gram negative) but ceftriazone for convinience - as it is once a day dose and lower risk of PICC line occlusion.
3. infected prosthetics - combination therapy with flucoxicillin + ciprofluoxacin or rifampicin. better chance of killing organism due to presence of biofilm. options: surgery to remove joint then IV antibiotics until aseptic then joint replacement takes 9 months or lifelong prophalaxis.
4. ???Culture negative - cipro, rifampicin(treat myco), fusedic acid.