When the Beatles wrote “I Wanna Hold Your Hand” in the coquettish year of 1963 they were not singing about the flexor digitorum superficialis, but this extrinsic flexor muscle, a master puppeteer of the fingers at the proximal interphalangeal joints and crucial in finger muscle anatomy, has been inspiring amorous hearts to link phalanges and palmer aponeuroses in expressions of school girl love for decades.
This anterior muscle of the forearm originates at the medial epicondyle of the humerus, better known as the bottom of your upper arm bone, and at the radius and ulna, the two bones that form the structure of the forearm. It splits into four tendons that insert on anterior margins on the bases of the middle phalanges of the four fingers, also known as your second knuckles. The most notable action of the flexor digitorum superficialis muscle, besides playing Cupid, is to flex the proximal interphalangeal joints, essentially creating that curling in of the fingers around a lovers hand.
By now I am sure you understand why this muscle is so important, if not only for sustaining your romantic thrills, the flexor digitorum superficialis is also responsible for taking care of details such as tying ribbons, unbuttoning buttons, playing the acoustic guitar, picking up seashells along the beach, and typing long lost love letters…just to mention a few.