A bruise is a common skin injury that results in a discoloration of the skin. Blood from damaged blood vessels deep beneath the skin collects near the surface of the skin resulting in what we think of as a black and blue mark.
Bruises can occur in some people who exercise rigorously, such as athletes and weight lifters.
These bruises result from microscopic tears in blood vessels under the skin. Unexplained bruises that occur easily or for no apparent reason may indicate a bleeding disorder, especially if the bruising is accompanied by frequent nosebleeds or bleeding gums. Often, what are thought to be unexplained bruises on the shin or the thigh, for example, actually result from bumps into a bedpost or other object and failing to recall the injury. Bruises in elderly people frequently occur because their skin has become thinner with age. The tissues that support the underlying blood vessels have become more fragile.