A patient presents with thumb pain after twisting their thumb. What examination must be definitively conducted to prevent overlooking a common and significant injury?

The correct answer is B. In the case of a twisted thumb, it's crucial to examine the ulnar collateral ligament so as not to miss a 'Skier's Thumb' injury. 'Skier's Thumb' occurs due to damage to this ligament, which is pivotal for the stability of the thumb. The examination should ascertain whether the ulnar collateral ligament is tender on palpation and whether there's noticeable laxity when performing the stress test.