On routine physical examination, small children are commonly found to have bruises. The difficulty for physicians is to determine if the bruising is a result of normal activity or child abuse. Previous studies contend that a soft tissue injury in any child under nine months of age should raise the suspicion of abuse. However, small cohort numbers or an inconsistent description (lacerations, burns, abrasions versus bruises) of the injury limits the data from these studies. Sugar and colleagues conducted a study to determine the prevalence of bruises in infants and toddlers and to discover if gross motor development independently influences the likelihood that a child has bruises.

Children seen for well-child visits at six private practices and one urban clinic were enrolled in the study. The age range was newborn to 35 months. At the time of the visit, the physician noted the presence of bruises and marked the location on a body diagram. Also noted was whether the child had a known or suspected medical condition that could account for the bruise or if a nonaccidental injury was suspected. The child's developmental stage in regard to ambulatory ability was obtained from the parent or care-giver. Children were classified as “precruisers” (no upright ambulation); “cruisers” (ambulation holding onto another person's hands or furniture); and “walkers” (the ability to take at least two independent steps). Age parameters included three groups: precruisers younger than 15 months of age; cruisers six to 18 months of age; and walkers older than seven months of age. Children found to have a medical or reported nonaccidental cause for their bruises were ultimately excluded.

After exclusion criteria were applied, 942 children (463 boys and 479 girls) were enrolled in the study. Bruises were noted with equal frequency in boys and girls (93 of the boys and 105 of the girls) but were much more common in white children (23 percent) than in black children (8 percent).

The presence of a bruise correlated strongly with patient age and ambulatory status. In the precruiser group (younger than six months of age), only two infants of 366 had bruises, both located on the scalp. In children aged six to eight months, six of 107 had bruises (four precruisers and two cruisers). After nine months of age, the frequency of bruises increased considerably, to 10.5 percent (precruisers) and 19 percent (cruisers) in the nine- to 12-month group; 12.5 percent (precruisers), 33 percent (cruisers) and 46.9 percent (walkers) in the 12- to 14-month age group; 16.7 percent (cruisers) and 45.9 percent (walkers) in the 15- to 17-month age group; 49.4 percent (walkers) in the 18- to 23-month age group and 60.9 percent (walkers) in the 24- to 35-month age group. Bruising also correlated with the developmental stage: 51.9 percent of the walkers, 17.8 percent of the cruisers and only 2.2 percent of the precruisers were noted to have bruising. When analyzing developmental stage across the various age groups, children who were ambulating upright consistently had more bruising.

In the few precruisers who had bruising, the most common sites were the anterior tibia or knee, forehead and scalp. In the cruising and walking groups, the most common sites were the anterior tibia or knee, affecting 11.9 and 44.7 percent of these two groups, respectively. Overall, 93.1 percent of all bruises were over bony prominences. Uncommon sites for bruising were the back, forearm or face, with only 2 percent of the walkers having marks in these locations.

The authors conclude that infants younger than nine months of age who are nonambulatory rarely have bruises related to nonmedical conditions. Bruises in children younger than six months of age are exceedingly rare. If bruises are found on examination in these children, the possibility of physical abuse or a medical illness should be strongly considered. Bruises on atypical sites such as the buttocks, trunk, abdomen, feet or hands may also be related to abuse.