The carp metacarpal joint of the thumb is a distinguishing, yet notorious feature of the human opposable thumb. On the one hand, it is fittingly also known as the basal joint, since it is the “base” from which the thumb has a large range of motion, and therefore, permits the hand to perform many functions. On the other hand, its unique anatomic configuration, which allows this vital motion, also predisposes the basal joint to degeneration and arthritis.