Small - only identified by electron microscopy Not birefringent Clumps of crystals (shiny coins) under LM Alizarin red stain to detect calcium-containing crystals Acute inflammatory arthritis (young people) Milwaukee shoulder (older people)
Calcium oxalate crystals
bipyramidal and envelope shaped Stain with alizarin red Primary oxaluria (autosomal recessive) Kidney failure on hemodialysis
Cholesterol crystals
Very large Flat and rectangular shaped Notched corners Varying birefringence Rheumatoid arthritis
Corticosteroid crystals
Iatrogenic Strongly variably birefringent Polymorphic clumps, rods, or rhomboids May cause joint pain for several hours
Talc crystals
Iatrogenic Originate from latex gloves during arthrocentesis Strongly birefringent Maltese cross pattern
Free fat
oil-red-O - stains droplets red osmic acid - stains droplets black Most likely result of trauma (intra-articular fracture)
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