[Liquid lipid crystals-induced arthritis]

Liquid lipid crystals-induced arthritis crystals are a frequent cause of arthritis. They are disclosed by the microscopic examination of the synovial fluid. They are usually made of monosodium urate, calcium pyrophosphate or apatite. Liquid lipid crystals have a spherical shape with an aspect of Maltese crosses and a positive birefringence. They are sometimes observed outside the leukocytes in rheumatoid or post-traumatic effusions. In some cases, they constitute the solely cause explaining the arthropathy. Then, they are numerous and located in and outside the cells. This observation reports on the case of a 50 year-old woman having developed this type of arthritis related to a right knee hemarthrosis. Awareness of this pathology may be useful because its evolution is usually good with a non-steroidal anti-inflammatory drug or a local steroid infiltration after exclusion of an infectious origin of the effusion.