Symptoms and signs

• Acutely painful, swollen joint
• Warm, tender, swollen joint (+/- effusion)

Alert

• Assume patients with a short history of a hot, swollen, tender joint with restricted range of movement have septic arthritis even in the absence of a fever until proven otherwise
• Pyrexia may not be a feature of septic arthritis, especially in the elderly or Immunocompromised, or in patients with diabetes, renal failure or rheumatoid arthritis
• In patients with prosthetic joint and pyrexia of unknown origin (PUO) - consider prosthesis infection
• If patient has acute arthritis affecting more than one joint, discuss case with on-call rheumatologist

Investigations

Immediate

• Urgent joint aspiration prior to starting antibiotics - see Knee aspiration guideline
  • contact on-call orthopaedic team (bleep) for urgent joint aspiration +/- arthroscopic washout and further management. If prosthetic joint, orthopaedic team aspirate in theatre
• Synovial fluid
  • Gram stain and culture of synovial fluid
  • polarised light microscopy for crystals
• FBC, U&E, LFT, ESR, CRP
• Blood cultures - see Collection of blood culture specimens guideline
• Swab from any infected skin lesion
• Urine dipstick. If positive for nitrites and/or leucocytes, MSU
• If gonococci suspected, swab rectum, urethra and throat, and contact genitourinary medicine

Within 24 hr

• Serum uric acid
• X-ray of affected joint

Differential diagnosis

• Septic arthritis
• Crystal arthritis, including gout and calcium pyrophosphate crystal deposition (CPPD)
• Acute inflammatory arthritis (e.g. reactive arthritis or rheumatoid arthritis)
• Haemarthrosis

Supportive

• Adequate analgesia for joint pain
• Naproxen 500 mg single oral dose, then 250 mg oral 6-hrly (if not contraindicated)
  • add paracetamol 1 g oral 6-hrly if required
  • if pain is still not controlled, consider adding codeine or morphine - check BNF for dose
• Refer to physiotherapists for ice pack and splint on joint
• Rehydrate - see Adult fluid management guideline
• If patient already taking low-dose corticosteroids and septic arthritis likely, consider increasing dose to manage potential hypoadrenalism

Antimicrobial therapy

• Start as soon as joint aspirated
• Most common microbe causing septic arthritis is Staphylococcus spp (including MRSA), other causes include Steptococcus spp
• If patient immunocompromised or has prosthesis, contact consultant in infectious diseases or consultant microbiologist for advice
• If severe sepsis present, refer to Sepsis management guideline and treat with appropriate IV antimicrobials

Penicillin Allergy

• True penicillin allergy is rare
• Ask the patient and record what happened when they were given penicillin
• If any doubt about whether patient is truly allergic to penicillin, seek advice from a microbiologist or consultant in infectious diseases

Infection Control alerts

• Check for IC alert
• If IC alert not available, check previous 12 months of microbiology reports
• If MRSA present, treat as tagged for MRSA. See MRSA management
• If ESBL, MGNB, CARB present, treat as tagged for ESBL. See ESBL/MGNB/CARB management

• Pulse, BP, temperature 4-hrly until patient stable
• If using sodium fusidate or rifampicin, liver function tests weekly

Septic arthritis

• Supportive treatment, as above

• Refer to physiotherapists for passive exercise and rehabilitation
• Perform regular aspiration of the joint to dryness +/- arthroscopic lavage while a significant effusion persists
• If patient able to be managed at home and on IV antimicrobials, refer to outpatient antibiotic therapy service for IV antimicrobials at home

Review antimicrobial choice after Gram stain and after synovial fluid culture result

• If gonococci isolated and strain sensitive:
  • refer patient to genitourinary medicine
  • ceftriaxone 1 g IV or IM daily or if anaphylaxis to penicillin, ciprofloxacin 500 mg IV 12-hrly for 7 days
    • total treatment 14 days (including IV and oral)
  • if strain resistant to ciprofloxacin, contact consultant microbiologist
  • 24-48 hr after symptoms improve, switch to ciprofloxacin 500mg oral 12-hrly
• If no bacteria isolated, consider stopping antimicrobials but note that neither the absence of organisms on Gram stain nor a negative subsequent synovial fluid culture excludes the diagnosis of septic arthritis. Discuss with rheumatology team 

Failure to respond to therapy

• Reconsider diagnosis
• Repeat synovial fluid culture and light microscopy, and blood cultures 
• If no response within 48 hr, contact rheumatology team

Duration of antimicrobial therapy

• Do not stop treatment until symptoms (e.g. fever) and signs (e.g. joint effusion) resolve, and WBC and CRP return to normal
• If infection likely or proven, continue IV antimicrobials for at least 2 weeks.
• If good clinical response to IV therapy, CRP falling and good information on organism and its sensitivities after that time, switch to oral therapy
• contact consultant microbiologist if required
• Continue antimicrobials for a 4-6 weeks total. Do not stop treatment until symptoms (e.g. fever) and signs (e.g. joint effusion) resolve, and WBC and CRP return to normal

Confirmed crystal arthritis (gout or CPPD)

• Crystal arthritis is confirmed by microscopic identification of urate (negatively birefringent) or CPPD (positively birefringent) crystals in synovial fluid
• Rehydrate - see Adult fluid management guideline
• Consider stopping diuretics
• If no contraindications, start NSAID (e.g. naproxen 750 mg single dose then 250 mg oral 8-hrly) at maximum dose or colchicine in doses of 500 microgram 2-4 times daily (max 6 mg per course)
• choice of first-line agent will depend on patient preference, renal function and co-morbidities
• prescribe any patients on non-selective NSAIDs or cyclooxygenase-2 inhibitors (coxibs) a gastro-protective agent
• Intra-articular and systemic corticosteroids are effective in acute crystal arthritis but use only under rheumatologist guidance
• In difficult or resistant cases, contact rheumatology team

• If patient already under follow-up because of arthritis, review existing follow-up arrangements
• For septic arthritis, follow-up under orthopaedics
• For other forms of arthritis refer to rheumatology