What is the most likely diagnosis for swelling of the thenar eminence and inability to move the thumb?

The scenario presented describes swelling of the thenar eminence and an inability to move the thumb, which suggests a specific type of injury to the thumb. A Bennett fracture, which is a fracture of the base of the first metacarpal bone, is particularly relevant in this context. This type of fracture can lead to dislocation at the carpometacarpal joint of the thumb and results in the characteristic swelling in the thenar eminence. The trauma often involves axial loading, and symptoms include pain, swelling, and limited motion of the thumb due to the fracture's impact on the joint's stability and functionality.

In contrast, a scaphoid fracture typically presents with wrist pain rather than localized swelling in the thenar eminence, and while it can affect thumb mobility indirectly, it wouldn't specifically cause swelling of that area. Gamekeeper's thumb refers to a sprain of the ulnar collateral ligament of the thumb, which might limit mobility but doesn’t usually present with significant swelling of the thenar eminence. Finkelstein's test is a clinical examination used to diagnose De Quervain's tenosynovitis, which involves pain on thumb movement rather than swelling, and does not relate to an inability to move the thumb due