What type of injury is best described by a clean edge and no bruising?

The best choice for an injury characterized by a clean edge and no bruising is an incision. An incision is typically produced by a sharp instrument, such as a knife or scalpel, resulting in a smooth, linear wound with well-defined edges. The lack of bruising is significant because it indicates that the underlying tissues were not crushed or damaged by blunt force, which often accompanies other types of injuries like lacerations or contusions.

In contrast, a stab wound, while it can have similar characteristics to an incision, usually involves a deeper penetration that may not always result in clean edges and can also be associated with bruising depending on the angle of the stabbing instrument. Lacerations are caused by blunt force trauma that results in tearing of the skin and tissues, leading to irregular edges and typically more significant bruising due to the damage to blood vessels. Contusions, or bruises, are not wounds per se but areas of skin discoloration caused by bleeding beneath the skin following blunt trauma, thus completely unrelated to the clean edges described in the question.

Therefore, an incision is the most accurate representation of the injury described due to its clean appearance and absence of bruising.