The flexor digitorum profundus, also called the “digital ulnar forearm”, is a group of muscles in the forearm that flexes the small digits (also called fingers) at their tips. Because it is buried in the skin, it does not have a tendon. It is believed that the three muscles make a perfect team to help flex the digits when the skin is stretched. Together, the flexor digitorum longus, digital medius, and pronator profundus form a deep layer of deep forearm muscles known as the extensor carpi radialis.

Understanding the Functions

This muscle helps extend the flexor digitorum profundus from the forehand side to the palm side. The long muscles insert onto the forearms that are in front of the fingers. It seems that they extend onto the inner side of the palm as well. The forearms then gradually extend out to the sides of the hands. This action helps with dexterity, allowing us to manipulate small objects with ease.

The nerve supply to this muscle is through the Lateral Epicondyle. The nerve may not be as strong as the nerve supply to other muscles in our forearms, which explains why we cannot feel the flexor digitorum profundus when it is contracted. When the muscle innervates, it is caused by the nerve in our elbow being pinched between the tendons. When this occurs, the tendons close over the nerve causing pain, tingling or numbness in certain parts of the body. This can happen to the thumb as well as the index and middle fingers.

Levator Aponeurosis & Flexor Latus

There are two important muscles that make up the flexor digitorum profundus. These muscles are the levator aponeurosis and the flexor latus. The muscle belly of the muscle is made up of tendons, bursa and a muscle called the supraspinatus. The tendons insert onto the bottom of the humerus (the upper arm bone) and onto the base of the index finger.

Long bones such as those of the skull and vertebrae are attached to the ends of the bones that form the limbs by ligaments, tendons and muscles. The tendons of these bones enable them to stretch, bend and move into a number of different positions. The most common are the ulnar groove. The Digitari muscles that attach to the ends of the long bones are also called the Digitari flexor muscles.

Causes of Weakness

The internal structures of the Digitari flexor tend to become weak with age and with repeated trauma to the surrounding area, resulting in pain, swelling and deformity. The Digitari flexor tendons actually divide at the base of the digit. This division makes it easy for one muscle to supply blood supply to the weak ulnar artery and the adjacent weak ulnar artery (thereby depriving the ulnar artery of blood supply). This results in constant pain under the nail bed on the palm side of the foot.


When the digital flexor muscle is injured or suffers from age-related weakness, the blood supply to the ulnar artery is cut off. This cuts off the blood supply to the small intestine. This can then cause vitamin D deficiency and resultant osteoporosis. Inflammation, irritation and swelling in the tendon areas can make it difficult to heal. The process of tendonitis may affect the normal functioning of the digitorum as well, as it can lead to repetitive strain injury and abnormal scar formation. As the ulnar artery supplies blood to the digiterum, a vicious cycle begins.

The common forearm pain is often described as radiating, spreading, non-specific, or symmetrical. It usually affects only one side of the hand or the little finger and can be accompanied by weakness in other flexor muscles such as the medial or the mid forearm muscles. The ulnar artery and the common interosseous artery are both involved here, as they are connected to the digitorum profundus. The pain is usually felt when bending the wrist or when the weight of the body is applied to the affected area. In cases where the pain is located at the wrist’s juncture with the ulnar artery, it is called radial neuropathy.


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