What is the most likely working diagnosis for a 14-year-old patient who has proximal forearm pain and a positive fat pad sign on X-ray?

The most likely working diagnosis for a 14-year-old patient presenting with proximal forearm pain and a positive fat pad sign on X-ray is a radial head fracture. The fat pad sign indicates the presence of an effusion or bleeding in the joint, which often accompanies an injury to the elbow, such as a fracture of the radial head.

In this case, the radial head is particularly susceptible to fractures in adolescents due to falls or trauma. When an X-ray shows a positive fat pad sign, it suggests that while the fracture might not always be visible, there is damage in the region of the elbow, commonly associated with radial head fractures. This is a classic presentation, given the age of the patient and the mechanism of injury that typically involves falling onto an extended arm, leading to stress on the radial head.

The conditions listed in the other options do not adequately explain the specific symptoms or X-ray findings presented in this case. Ulnar nerve injury often has different symptomatology, such as tingling or numbness in the little finger, rather than pain indicative of a fracture. Medial epicondylitis is more associated with chronic overuse and usually presents with pain that is exacerbated by specific movements rather than a specific traumatic event and typically