Septic Arthritis

Key points

• Most common organism overall: Staphylococcus aureus; consider Neisseria gonorrhoeae in sexually active young adults.
• Kocher criteria (a PAEDIATRIC hip score separating septic arthritis from transient synovitis, not an adult diagnostic rule): fever > 38.5ºC · non-weight bearing · raised ESR · raised WCC.
• Obtain synovial fluid BEFORE starting treatment.
• IV antibiotics covering Gram-positive cocci — flucloxacillin, or clindamycin if penicillin-allergic · BSR/BOA/BSAC 'hot swollen joint' guidance: give IV for up to 2 weeks or until signs improve, then oral for 4 weeks (about 6 weeks in total), guided by symptoms, signs and acute-phase response.
• Needle aspiration to decompress the joint; arthroscopic lavage may be required.