The Flexor Pollicis Longus is a muscle located in your forearm. It plays a crucial role in the movement of your thumb. Specifically, this muscle helps you bend the thumb inward toward your palm, a motion known as flexion. This movement is essential for gripping objects and performing tasks that require fine motor skills, like writing or buttoning a shirt.
The muscle originates from the middle part of the radius, one of the two bones in your forearm, and from the interosseous membrane, which is a thin, fibrous sheet that connects the radius and the ulna (the other bone in your forearm). It extends down the forearm and passes through a tunnel at the wrist called the carpal tunnel. Here, it becomes a tendon, which is a strong, fibrous connective tissue. This tendon then inserts into the base of the distal phalanx, the bone at the tip of your thumb.
Due to its path from the forearm through the wrist to the thumb, the Flexor Pollicis Longus is crucial for the thumb’s full range of motion. Its effective functioning is vital for hand strength and dexterity, making it important in both everyday and specialized activities. If this muscle or its tendon becomes inflamed or irritated, it can lead to pain and difficulty in thumb movements, affecting your ability to perform tasks that rely on your grip. Proper exercises, stretching, and sometimes medical intervention are necessary to maintain or restore the health and functionality of this muscle.