A 23 year old professional baseball player presents at the E…

A 23 year old professional baseball player presents at the ER with swelling in his right knee. He has had chronic problems with this knee and has undergone multiple diagnostic and treatment procedures. A synovial fluid sample is collected by arthrocentesis and the following results are obtained: Color- yellow, Clarity- slightly cloudy, viscosity-normal, specific gravity: >1.040, WBC count 950 cells/?L, monocytes 65%, lymphocytes 17%, neutrophils 18%, rare birefringent prism shaped crystals. What is the most likely identity of the crystals?