Accidental childhood bruises are usually limited to extensor surfaces and bony prominences. They are usually the result of falls in infants or toddlers with unsteady motor skills, or in older children during high-energy play activities (e.g., playground falls, sports injuries).
Bruises to the trunk, flexor surfaces, face, ears, genitals, or to diapered areas are less common after accidental childhood injuries, and should be carefully evaluated. The parent or guardian should be questioned about how the injury occurred, and the explanation should be compared to the child's developmental capabilities and to the amount of impact energy implied by the explanation.
Accidental bruises are usually the result of falls, so bruises in infants who have not started crawling or walking are suspicious for abuse. A classic study on this topic includes the sentence "Those who don't cruise rarely bruise."
Patterned bruises are very suspicious for inflicted injury. If the outline of a hand, fingers, or of an object can be seen, the injury should be carefully documented.