Radial head subluxation (Nursemaid elbow)

A 4-year-old girl is brought to the emergency department for acute onset left elbow pain. She was playing in her sandbox when her parent pulled her by the arm to take her inside. Vitals are within normal limits. Examination reveals a young girl who keeps her hand in a pronated and extended position. Any manipulation of the arm causes the girl to cry. There is no swelling or deformity. The physician hyperpronates the forearm, resulting in a click with immediate cessation of pain and resumption of the patient using her arm. Which of the following best describes the etiology of this patient’s condition?