The appearance of purple (violaceous) plaques on the knees may be associated with dermatomyositis. Typically, most lesions associated with other diseases are red (erythematous).
Review Date: 2/11/2013 Reviewed By: Reviewed by: Ariel D. Teitel, MD, MBA, Clinical Associate Professor of Medicine, NYU Langone Medical Center. Review provided by VeriMed Healthcare Network. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.