Electron microscopic study of depot corticosteroid crystals with clinical studies after intra-articular injection.

Depot corticosteroid crystals and their in vivo handling after intra-articular injection have not been studied by electron microscope (EM). We therefore injected 20 mg of either prednisolone tebuate or triamcinolone hexacetonide into knee joints of 7 patients with osteoarthritis and painful effusions. Six patients had a rise in the synovial fluid leukocyte counts, but only 1 patient had clinical evidence of a post-injection flare. Scanning and transmission EM revealed intra- and extracellular crystals 24 hours and 1 week after the initial injection. These combined EM studies provide an adjunct to compensated polarized microscopy in differentiation of depot steroid from other crystals.