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.
Acute septic arthritis, infectious arthritis, suppurative arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typically include redness, heat and pain in a single joint associated with a decreased ability to move the joint. Onset is usually rapid. Other symptoms may include fever, weakness and headache. Occasionally, more than one joint may be involved, especially in neonates and younger children. In neonates, infants during the first year of life, and toddlers, the signs and symptoms of septic arthritis can be deceptive and mimic other infectious and non-infectious disorders.In children, septic arthritis is usually caused by non-specific bacterial infection and commonly hematogenous, i.e., spread through the bloodstream. Septic arthritis and/or acute hematogenous osteomyelitis usually occurs in children with no co-occurring health problems. Other routes of infection include direct trauma and spread from a nearby abscess. Other less common cause include specific bacteria as mycobacterium tuberculosis, viruses, fungi and parasites. In children, however, there are certain groups that are specifically vulnerable to such infections namely preterm infants, neonates in general, children and adolescence with hematologic disorders, renal osteodystrophy and immune-compromised status. In adults vulnerable groups include an artificial joint, prior arthritis, diabetes and poor immune function. Diagnosis is generally based on accurate correlation between history-taking and clinical examination findings and basic laboratory and imaging findings like joint ultrasound.In children septic arthritis can have serious consequences if not treated appropriately and timely. Initial treatment typically includes antibiotics such as vancomycin, ceftriaxone or ceftazidime.