What physical examination finding is most concerning for a 2-year-old with an apparent arm injury?

Resistance to movement at the elbow in a 2-year-old with an arm injury is particularly concerning and may indicate several underlying issues that require immediate attention. This finding suggests possible significant pain or joint involvement, which could be associated with a fracture, dislocation, or other serious injury. In young children, the inability or unwillingness to move a limb often points to a more severe injury, as they may not accurately communicate their symptoms or the extent of their pain.

While tenderness over the shoulder, obvious deformity of the elbow, and swelling of the wrist are also important findings, they may not indicate an immediate or life-threatening condition as clearly as resistance to movement. These findings can vary in significance depending on the context and the child's behavior; however, an unwillingness to move the affected extremity typically raises concern for painful or serious underlying pathology that necessitates further evaluation, such as imaging. Thus, this specific finding warrants closer investigation to rule out significant injuries in the context of a pediatric arm injury.