A bruise occurs when a force causes blood vessels to break. Blood leaks into areas under the skin, resulting in pain, swelling, and skin discoloration.
Update Date 5/1/2011
Updated by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.