What compound structure is stressed when testing a patient's elbow to resist a Valgus force?

When testing a patient's elbow for resistance to a valgus force, the medial collateral ligament (MCL) is the primary structure that is stressed. A valgus force occurs when the forearm is pushed laterally relative to the upper arm, which puts tension on the inner (medial) side of the elbow. The MCL, which stabilizes the elbow joint on this side, is responsible for resisting excessive valgus forces.

This ligament consists of three bundles that work together to provide stability during activities that involve throwing or when the elbow is subjected to sideways forces. If the MCL is strained or injured, it can lead to instability and increased risk of injuries in athletes, particularly in sports that require repetitive overhead motions.

The other structures mentioned, such as the lateral collateral ligament, ulnar nerve, and radial nerve, do not primarily function to resist valgus forces at the elbow. The lateral collateral ligament is more involved in resisting varus forces, while the ulnar and radial nerves are primarily responsible for innervating muscles and sensory functions in the arm and hand. Hence, when considering the specific action of resisting a valgus force at the elbow, the medial collateral ligament is the correct answer.