Muscles in The Finger
By Lily Condy, CHT, OT
Muscles in The Finger
Did you know that the finger doesn’t contain any muscles? All the muscles that control finger motion are located in the hand and forearm. The fingers perform 5 basic movements: flexion, extension, abduction, adduction, and circumduction. Each finger is able to move independently of one another, but coordinate to work well as a team.
Each finger is made up of three bones known as the proximal, middle, and distal phalanges (starting at the hand and moving outward). The thumb has just two bones, the proximal and distal phalanx. The closest set of knuckles are known as the metacarpal phalangeal joints (MCP), and then moving distally are the proximal interphalangeal joint (PIP) and the distal interphalangeal joint (DIP).
Finger flexion is what happens when you make a fist. Flexion is the strongest movement that the fingers perform and is used during grasp and pinch. Each finger has two muscles involved in flexion; flexor digitorum profundus, which attaches to the distal phalanx, and flexor digitorum superficialis, which attaches to the middle phalanx. These long flexors originate near the elbow and run through the forearm. The lumbricals control flexion of the proximal phalanx and are the only muscles in the body that do not attach to bone. They originate from the flexor digitorum profundus and attach to the extensor hood.
Finger extension occurs when you straighten out your hand. Extension happens when releasing an item from your grasp, pointing a finger, or pushing up from a flat surface. The muscles that control finger extension are called the extensor digitorum communialis. These muscles originate near the elbow, run through the back of the forearm, and insert onto the proximal phalanx. The central tendon continues distally and inserts at the middle phalanx, and the lateral bands insert onto the distal phalanx. This complex system acts to fully extend the digit. The extensor hood surrounds the metacarpal phalangeal joints and receives tendinous fibers from the interossei and lumbrical muscles. The lumbricals also help to extend the PIP joints.
Each finger is capable of abduction and adduction. These terms mean to move away and bring together, such as spreading your fingers apart and squeezing them back together again. These motions are controlled by palmar and dorsal interossei, which connect to the extensor hood to control movement.
Lastly, the thumb has its very own set of muscles to perform functions which make the human hand so unique. There are two flexors, flexor pollicis longus and flexor pollicis brevis, two extensors, extensor pollicis longus and extensor pollicis brevis, and two abductors, abductor pollicis longus and abductor pollicis brevis. These muscles flex, extend, and abduct the thumb, respectively. There is also a set of opponens muscles, which move the thumb out toward the small finger, allowing for a cylindrical grip around a soda can, for example. Lastly, the thumb has an adductor pollicis, which contributes to the pinching grip. Some of these muscles originate in the forearm and some originate from within the hand. Working together, these muscles are able to circumduct the thumb.
With so many different muscles and systems controlling the fingers, it’s no wonder that a small injury can have a significant impact on function. Selecting health care professionals who specialize in hand and finger injuries is important in order to maximize your success!
JOI Physicians are currently offering ASAP fracture and injury care. Further, this is a new option for patients who would like to avoid the emergency room if they have suffered a fracture or soft tissue injury. To learn more about this service, read this article about fracture and injury care. Make an appointment by calling (904)JOI-2000.
Please do not hesitate to call JOI for your medical needs. Further, we have surgeons that can help diagnosis your tear and therapy staff waiting to help rehab you back to full health! Please call JOI-2000 or click the banner below to schedule with one of our specialists.
Written by: Lily Condy, CHT, OT