The differential diagnosis of septic arthritis is broad and challenging. First, it has to be differentiated from acute hematogenous osteomyelitis. This is because the treatment lines of both conditions are not identical. Noteworthy, septic arthritis and acute hematogenous osteomyelitis can co-occur. Especially in the hip and shoulder joints their co-occurrence is likely and represents a diagnostic challenge. Therefore, physicians should have a high suspicion index in that regard. This is because in both the hip and shoulder joints the metaphysis is intra-articular which in turn facilitates the spread of hematogenous osteomyelitis into the joint cavity. Conversely, joint sepsis may spread to the metaphysis and induce osteomyelitis. Acute exacerbation of juvenile idiopathic arthritis and transient synovitis of the hip both of which are non-septic conditions may mimic septic arthritis. More serious and life-threatening disorders as bone malignancies e.g. Ewing sarcoma and osteosarcoma may mimic septic arthritis associated with concurrent acute hematogenous osteomyelitis. In this regard, Magnetic resonance imaging may play an important role in the differential diagnosis. Joint aspiration In children, joint synovial fluid aspiration techniques aim at isolating the infectious organism by culture and sensitivity analysis. Cytological analysis of the joint aspirate can point to septic arthritis. However, a negative culture and sensitivity test does not rule out the presence of septic arthritis. Various clinical scenarios and technique-related factors may impact the validity of results of the culture and sensitivity. Additionally, results of cytological analysis, though important, should not be interpreted in isolation of the clinical settings. Synovial fluid from a knee with septic arthritis In the joint fluid, the typical white blood cell count in septic arthritis is over 50,000-100,000 cells per 10−6/l (50,000-100,000 cell/mm3); where more than 90% are neutrophils is suggestive of septic arthritis. For those with prosthetic joints, white cell count more than 1,100 per mm3 with neutrophil count greater than 64% is suggestive of septic arthritis. However, septic synovial fluid can have white blood cell counts as low as a few thousand in the early stages. Therefore, differentiation of septic arthritis from other causes is not always possible based on cell counts alone. Synovial fluid PCR analysis is useful in finding less common organisms such as Borrelia species. However, measuring protein and glucose levels in joint fluid is not useful for diagnosis. The Gram stain can rule in the diagnosis of septic arthritis, however, cannot exclude it. Synovial fluid cultures are positive in over 90% of nongonoccocal arthritis; however, it is possible for the culture to be negative if the person received antibiotics prior to the joint aspiration. Cultures are usually negative in gonoccocal arthritis or if fastidious organisms are involved. If the culture is negative or if a gonococcal cause is suspected, NAAT testing of the synovial fluid should be done. Positive crystal studies do not rule out septic arthritis. Crystal-induced arthritis such as gout can occur at the same time as septic arthritis. A lactate level in the synovial fluid of greater than 10 mmol/l makes the diagnosis very likely. Blood tests Laboratory testing includes white blood cell count, ESR and CRP. These values are usually elevated in those with septic arthritis; however, these can be elevated by other infections or inflammatory conditions and are, therefore, nonspecific. Procalcitonin may be more useful than CRP. Blood cultures can be positive in up to half of people with septic arthritis. Imaging Imaging such as x-ray, CT, MRI or ultrasound are nonspecific. They can help determine areas of inflammation but cannot confirm septic arthritis. When septic arthritis is suspected, x-rays should generally be taken. This is used to assess any problems in the surrounding structures such as bone fractures, chondrocalcinosis, and inflammatory arthritis which may predispose to septic arthritis. While x-rays may not be helpful early in the diagnosis/treatment, they may show subtle increase in joint space and tissue swelling. Later findings include joint space narrowing due to destruction of the joint. Ultrasound is effective at detecting joint effusions. CT and MRI are not required for diagnosis; but if the diagnosis is unclear or the joints are hard to examine (ie.sacroiliac or hip joints); they can help to assess for inflammation/infection in or around the joint (i.e. Osteomyelitis), bone erosions, and bone marrow oedema. Both CT and MRI scans are helpful in guiding arthrocentesis of the joints. Differential diagnosis * Crystal induced arthritis such as gout or pseudogout * Inflammatory arthritis * Rheumatoid arthritis * Seronegative spondyloarthropathy such as ankylosing spondylitis or reactive arthritis * Traumatic arthritis due to hemarthrosis, fracture or foreign body * Osteoarthritis
complications of Gonorrhea
complications of Chlamydia
complications of Trichinosis
symptom of Chlamydia
complications of Campylobacteriosis
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symptom of Rubella
complications of Roseola