Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 20-35: Nongonococcal Acute Bacterial (Septic) Arthritis + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Acute onset of inflammatory monarticular arthritis, most often in large weight-bearing joints and wrists Common risk factors include previous joint damage or injection drug use Infection with causative organisms commonly found elsewhere in body Joint effusions are usually large; white blood cell counts commonly > 50,000/mcL +++ General Considerations ++ Most often due to hematogenous seeding of the joint; direct inoculation from penetrating trauma is rare Key risk factors are Bacteremia (eg, injection drug use, endocarditis, infection at other sites) Damaged (eg, from rheumatoid arthritis) or prosthetic joints Compromised immunity (eg, advanced age, diabetes mellitus, advanced chronic kidney disease, alcoholism, cirrhosis, or immunosuppressive therapy) Loss of skin integrity (eg, cutaneous ulcer or psoriasis) Staphylococcus aureus is the most common cause of nongonococcal septic arthritis, accounting for about 50% of all cases Methicillin-resistant S aureus (MRSA) and group B streptococcus are frequent and important causes of septic arthritis Gram-negative septic arthritis is seen in injection drug users and in other immunocompromised patients Staphylococcus epidermidis is the usual organism in prosthetic joint septic arthritis + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Acute onset, with pain, swelling, and heat of affected joint—most frequently the knee Unusual sites, such as the sternoclavicular or sacroiliac joint, can be involved in injection drug users Chills and fever are common (but absent in up to 20% of patients) Infection of the hip usually does not produce apparent swelling but results in groin pain greatly aggravated by walking More than one joint is involved in 15% of cases; risk factors include rheumatoid arthritis, associated endocarditis, and infection with group B streptococci Polyarticular septic arthritis is uncommon except in patients with rheumatoid arthritis or with group B streptococcal infections Manifestations of prosthetic joint infection are influenced by whether the infection is early (≤ 3 months after surgery), delayed (3–12 months after surgery), or late (> 12 months after surgery) Early infections Acute redness and swelling Usually caused by S aureus and gram-negative organisms Delayed infections Pain is common but only 50% will have fever Most commonly caused by less virulent organisms, such as coagulase-negative staphylococcus, Proprionibacterium acnes, and enterococci Late infections Acute pain, swelling and fever Often caused by hematogenous seeding of S aureus, gram-negative bacilli, and hemolytic streptococci +++ Differential Diagnosis ++ Gout and pseudogout are excluded by the failure to find crystals on synovial fluid analysis Chronic Lyme disease commonly manifests as inflammatory monarthritis of the knee, but the synovial fluid is Gram stain and culture negative Acute rheumatic fever commonly involves an inflammatory migratory oligoarthritis Pyogenic arthritis may be superimposed on other types of joint disease, notably rheumatoid arthritis + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Blood cultures are positive in approximately 50% of patients The leukocyte count of the synovial fluid is always inflammatory (> 2000/mcL), usually exceeds 50,000/mcL and often is > 100,000/mcL, with ≥ 90% polymorphonuclear neutrophils Gram stain of the synovial fluid is positive in 75% of staphylococcal infections and in 50% of gram-negative infections +++ Imaging Studies ++ Radiographs are usually normal early in the disease, but evidence of demineralization may develop within days of onset MRI and CT are more sensitive in detecting fluid in joints that are not accessible to physical examination (eg, the hip) Bony erosions and narrowing of the joint space followed by osteomyelitis and periostitis may be seen within 2 weeks +++ Diagnostic Procedures ++ Joint aspiration is required to establish the diagnosis + Treatment Download Section PDF Listen +++ +++ Medications ++ If the likely causative organism cannot be determined clinically or from the synovial fluid gram stain, treatment should be started with broad-spectrum antibiotics effective against staphylococci (including MRSA), streptococci, and gram-negative organisms Initial treatment is to give vancomycin (1 g intravenously every 12 hours, adjusted for age, weight, and kidney function) plus a third-generation cephalosporin Ceftriaxone, 1–2 g intravenously daily (or every 12 hours if concomitant meningitis or endocarditis is suspected) Cefotaxime, 1–2 g intravenously every 8 hours Antibiotic therapy should be adjusted when culture results become available Duration of antibiotic therapy is usually 4–6 weeks Options for treating prosthetic joint infections Chronic suppression Debridement without removal of the prosthesis One- or two-stage exchange of the prosthesis +++ Surgery ++ Effective drainage is usually achieved through early arthroscopic lavage and debridement Open surgical drainage should be performed when Conservative treatment fails There is concomitant osteomyelitis requiring debridement The involved joint (eg, hip, shoulder, sacroiliac joint) cannot be drained by more conservative means +++ Therapeutic Procedures ++ Immobilization with a splint and elevation are used at the onset of treatment. Early active motion exercises as tolerated will hasten recovery + Outcome Download Section PDF Listen +++ +++ Complications ++ Bony ankylosis and articular destruction occur if treatment is delayed or inadequate +++ Prevention ++ There is no evidence that patients with prosthetic joints undergoing procedures should receive antibiotic prophylaxis to prevent joint infection unless the patient has a prosthetic heart valve or the procedure requires antibiotics to prevent a surgical site infection However, the American Academy of Orthopedic Surgeons advocates prescribing antibiotic prophylaxis for any patient with a prosthetic joint replacement undergoing a procedure that can cause bacteremia +++ Prognosis ++ With prompt antibiotic therapy and no serious underlying disease, functional recovery is usually good The mortality rate is 30% for patients with polyarticular infections and sepsis +++ When to Refer ++ Refer to an orthopedist if the infected joint is not easy to aspirate repeatedly (eg, hip) +++ When to Admit ++ Admit for presumed or confirmed septic arthritis + References Download Section PDF Listen +++ + +Coiffier G et al. Broad-range 16 s rDNA PCR in synovial fluid does not improve the diagnostic performance of septic arthritis in native joints in adults: cross-sectional single-center study in 95 patients. Clin Rheumatol. 2019 Jul;38(7):1985–92. [PubMed: 30850963] + +Gjika E et al. Two weeks versus four weeks of antibiotic therapy after surgical drainage for native joint bacterial arthritis: a prospective, randomised, non-inferiority trial. Ann Rheum Dis. 2019 Aug;78(8):1114–21. [PubMed: 30992295] + +Kapadia BH et al. Periprosthetic joint infection. Lancet. 2016 Jan 23;387(10016):386–94. [PubMed: 26135702] + +Khazi ZM et al. Arthroscopy versus open arthrotomy for treatment of native hip septic arthritis: an analysis of 30-day complications. Arthroscopy. 2019 Nov 19. [Epub ahead of print] [PubMed: 31757679] + +Mirza SZ et al. Diagnosing prosthetic joint infections in patients with inflammatory arthritis: a systematic literature review. J Arthroplasty. 2019 May;34(5):1032–6. [PubMed: 30846314]