The appearance of purple (violaceous) plaques on the knees may be associated with dermatomyositis. Typically, most lesions associated with other diseases are red (erythematous).
Richard J. Moskowitz, MD, Dermatologist in Private Practice, Mineola, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.