Recently an old female patient admitted to our hospital due to CHF and acute on CRF.Previously she ever accepted left hip replacement twice and bilateral knee replacemnt nearly 2 decades ago.Infection work-up was also performed.We excluded lung infection and UTI via a series of tests/lab but to gall bladder and left knee.At last we consider the infection source coming from left knee.According to PE,erythema and swollen of left knee was noted and arthrocentesis was performed post consultiing orthologist.Synovial analysis disclosed WBC greater than 50000/cumm with PMN predominantly(>75%) and sugar is lower(30mg/dl).This result is compatible with septic knee.Therefore I post up synovial fluid analysis to differentiate from different types of knee disease.
INTRODUCTION — Synovial fluid analysis may be diagnostic in patients with bacterial infections or crystal-induced synovitis. The white cell count, differential count, cultures, Gram stain, and crystal search using polarized light microscopy are the most valuable studies . Noninflammatory fluids generally have fewer than 2000 white blood cells/mm3, with fewer than 75 percent polymorphonuclear leukocytes .
INDICATIONS-- Suspected septic arthritis — The American College of Rheumatology (ACR) clinical guidelines committee suggests that unexplained inflammatory fluid, particularly in a febrile patient, be assumed to be infected until proven otherwise by appropriate culture.According to the ACR committee, synovial fluid analysis should be performed in the febrile patient with an acute flare of established arthritis (eg, rheumatoid arthritis, osteoarthritis) to rule out superimposed septic arthritis.Repeated aspiration and synovial fluid analysis may be used to monitor the response of septic arthritis to treatment and may also be valuable for diagnosis of some cases of gout in which the initial aspirate does not have detectable crystals