HRUS of Both Forearms

The two sides of the forearm are the anterior (palmar or volar) surface and the posterior (dorsal) surface. The anterior/volar side faces the palm and contains the flexor muscles and main neurovascular structures. The posterior/dorsal side faces the back of the hand and contains the extensor muscles. These terms are used to describe injuries, muscle groups, and surface anatomy.

The axis of the forearm is an imaginary longitudinal line running from the center of the radial head proximally to the ulnar head (styloid process) distally. It serves as the pivot for pronation and supination, allowing the radius to rotate around the relatively fixed ulna so the palm can turn upward (supination) or downward (pronation).

Anomalous forearm muscles include absence or reversal of palmaris longus; accessory heads such as Gantzer’s muscle (accessory head of flexor pollicis longus or flexor digitorum profundus); anomalous slips of flexor digitorum superficialis/profundus; accessory pronator teres, flexor carpi radialis brevis, and multiple abductor pollicis longus/extensor pollicis tendons. These variants are often asymptomatic but can cause nerve or tendon compression or present as unexpected masses.

The seven forearm muscles commonly referenced (anterior/flexor group) are: pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. These mainly produce wrist and finger flexion and forearm pronation, contributing to grip strength and stabilization during hand tasks.

The arm is commonly divided into two parts: the upper arm and the forearm. The upper arm runs from shoulder to elbow and contains the humerus bone, while the forearm extends from elbow to wrist and contains the radius and ulna. Muscles, nerves, blood vessels, and joints in each part enable movement, strength, and sensation.

Train both forearm sides with flexion, extension and rotation: palms-up wrist curls, palms-down (reverse) wrist curls, hammer or reverse curls for brachioradialis, and dumbbell pronation/supination. Add grip work: farmer carries, plate pinches and static holds. Do two to four sets of eight to twenty reps, two to three times weekly, using progressive overload and adequate recovery to prevent overuse.