The opponens pollicis muscle is a triangular-shaped muscle in the hand. It is found on and below the thumb. This muscle rotates and flexes the thumb, which enables cupping of the palm. It is one of the muscles in the hand that allows our thumbs to be opposable. This muscle's main nerve comes from the recurrent branch of the median nerve in the hand. The blood supply for this muscle comes from the superficial palmar arch. The opponens pollicis muscle is one of three thenar muscles. These are a group of muscles found on the palm of the human hand, near the base of the thumb. The opponens pollicis muscle works with the other thenar muscles to control movement of the thumb. There are many conditions that can affect this muscle, such as overuse injuries, neuromuscular diseases, atrophy, lacerations, and myopathy. The opponens pollicis muscle is connected to the bones of the hand by opponens pollicis tendons; these tendons facilitate the opponens pollicis muscle to create the action known as opposition.