Nicolau syndrome is a rare adverse reaction to a variety of intra-muscular drug preparations. The typical presentation is pain around the injection site soon after injection, followed by erythema, livedoid patch, hemorrhagic patch, and finally, necrosis of skin, subcutaneous fat, and muscle tissue. The phenomenon has been related to the administration of a variety of drugs, including non-steroidal anti-inflammatory drugs, corticosteroids, and penicillin. We report a case with typical features associated with diclofenac injection for pain control in a patient who had undergone bilateral total knee arthroplasty. (Ann Dermatol 23(4) 501~503, 2011)