The flexor muscles are on the fleshy belly side of the forearm and attach to the bony prominence of the elbow closest to your body (medial epicondyle), to the two bones of the forearm and to the connective tissue between them. The finger flexors are arranged in two layers between and under the wrist flexors. The wrist flexors are arranged like the bread of a sandwich on either side of the forearm closest to the two bones (radius and ulna). The pronator teres and some of the finger flexors are nestled in the middle like the sandwich filling with the remainder of the finger flexors spread underneath.
The function of the finger flexors is to close the hand (or individual fingers) around an object or to make a fist. The superficial layer is more specific to the middle joint of the fingers and the deep layer to the tip joint, but they assist each other. The function of the wrist flexors is to bend the hand toward the forearm (flexion) or to the right and left (deviation). Wrist and finger flexors assist each other and they all work together in forceful gripping motions. Even the extensor muscles get involved in these actions.
Symptoms of dysfunction occur when using scissors or pruners, especially when forceful or repeated use is required. Any cupping motion like squeezing a hair clip can be painful. Gripping a mouse can cause chronic tension. Drying hair using a brush and hair dryer can affect both hands and arms. Pulling weeds can be painful or any strong pulling and twisting motion with the hands in construction, even twisting a sticky doorknob. Driving when tense, gripping the steering wheel with a flexed wrist can aggravate the muscles.
Local pain from these muscles can be generated by dysfunction or injury to the muscles themselves, systemic factors like lack of blood or oxygen, toxic pain from accumulated chemicals and waste or irritation of the ulnar nerve near the elbow.
Dysfunction would be from spasm, weakness, and hyperactivity, but mostly from Trigger Points (TrPs). Referred pain from these hypersensitive nodules in the finger flexors goes down into the individual fingers and can feel like it’s shooting out the fingertips. TrP pain from the wrist flexors is felt mostly along the inner crease or sides of the wrist. Other symptoms are a weak or painful grip, pain bending the wrist, “golf (inner) elbow,” difficulty bending the fingers and “trigger finger” or “locking finger.” Referred pain can also come from the pectoralis minor, latissimus dorsi and serratus posterior superior muscles of the upper body.
In making decisions about the causes of a patient’s arm and hand pain, local dysfunction should be differentiated from Trigger Point symptoms, but both are usually present simultaneously.