Routes of Spread: Common routes of spread is hematogenous followed by direct inoculation (trauma or localised spread from a surrounding soft tissue infection)
Common Joints - Knee>Hip>Shoulder>Elbow
Risk Factors for Septic Arthritis (More abnormal joint, more likely Septic Arthritis)
- Bacteremia/systemic infection
- IVDU (may have sternoclavicular and sternomanubrial joint involvement)
- Overlying skin infection
- Diabetes Mellitus
- Prosthetic joints
- Elderly, Immunocompromised states
- Recent joint surgery or procedure
- Staph Aures 40%
- Streptocossus 30%
- GNB 20%
- Gonococcal arthritis - M. Presents as migratory polyarthritis and may involve several joints (wrist, knee and ankles), or include a rash/tenosynovitis.
- Typical - Swollen, Red, Immobile and Tender joint
- Joint tenderness has sensitivity approaching 100%
- Fever is seen only in about 50%
- ocal tenderness and pain limited to specific movements on an active range of motion testing is more typical of periarticular inflammation (skin, bursa, tendons).
- Synovial Fluid Analysis - Synovial fluid with a WBC count > 50,000/mm with a polymorphonuclear cell count > 90%. However, in culture-proven septic arthritis, this WBC count is reached only in 50 – 75% of cases. Therefore, . A synovial fluid WBC count >100,000/mm is more specific. 15,000 cells/μL
- Use CRP/ESR/WCC with caution - Normal levels cannot rule out septic arthritis
- septic arthritis (sensitivity only 50-60%). Culture remains the most sensitive test (>90%).
- Presence of crystals shouldnot be used to rule out septic arthritis. Gout and Septic Arthritis can co-exist in the same joint.
- Joint aspiration
- Empiric Antibiotics (should provide gram-positive and gram-negative coverage)
- Orthopedic Referral consultation
- More abnormal joint, more likely Septic Arthritis
- Immunocompromised patients often have polyarticular involvement and present atypically.
- Sudden onset of pain is more suggestive of intrinsic joint pathology, such as septic arthritis.
- Serum blood tests do not rule out septic arthritis
- If suspicion is still high after equivocal or dry tap, admit the patient and initiate empiric IV antibiotics while the synovial culture results