What is the most likely diagnosis for a child who refuses to use their arm after being pulled up by their hand?

The situation described involves a child who is hesitant to use their arm after being pulled up by the hand. This scenario typically indicates a subluxation of the head of the radius, commonly referred to as a "pulled elbow." This occurs when a force is applied to the arm, causing the radius to slip out of its normal position at the elbow joint.

In young children, especially those under the age of five, their ligaments are usually loose, making them more susceptible to such injuries. The mechanism of injury fits perfectly with the circumstance described—pulling a child up by the hand can easily create enough force to subluxate the radial head.

The clinical presentation usually includes an immediate refusal to use the arm, and the child may also exhibit a protective posture, keeping the arm by their side. Treatment typically involves a simple maneuver to reduce the subluxation, after which the child usually regains full function of the arm without any long-term complications.

This diagnosis aligns closely with the child’s behavior and the mechanism of injury described, providing a clear rationale for why this is the most likely diagnosis in this case.