Forearm
Region of the upper limb between elbow and wrist.
The forearm is the region of the upper limb between the elbow and the wrist. It contains two long bones, the radius and the ulna, and is covered by skin, with the anterior surface usually less hairy than the posterior surface. The forearm contains many muscles, including flexors and extensors of the wrist and digits, and is divided into two fascial compartments.
- Bones
- Radius and ulna
- Joints
- Proximal and distal radioulnar joints, elbow joint, wrist joint
- Nerves
- Median, radial, and ulnar nerves
- Arteries
- Radial and ulnar arteries
- Veins
- Cephalic, median antebrachial, and basilic veins
- Compartments
- Anterior (flexors) and posterior (extensors)
Lore & Background
The forearm is homologous to the crus, the region of the leg between the knee and ankle. The interosseous membrane connects the radius and ulna. The forearm can be flexed and extended at the elbow, and pronated and supinated at the elbow and distal radioulnar joint.
Reader's Guide
The forearm is significant as a distinct anatomical region, distinguished from the arm (upper arm) in technical anatomy. Its two bones, radius and ulna, form the radioulnar joints and articulate with the humerus and wrist. The forearm's muscles are organized into anterior flexor and posterior extensor compartments, supplied by the median and radial nerves respectively, with the ulnar nerve also running its length. The radial and ulnar arteries supply blood, and superficial veins like the cephalic and basilic are used for venipuncture, though the cubital fossa is preferred. Fractures may involve the ulna, radius, or both; torus fractures in children are better treated with splinting than casting. Hereditary multiple exostoses can cause forearm deformities due to growth disturbance of the epiphyses.
Did You Know?
- The forearm contains two long bones: the radius on the lateral side and the ulna on the medial side.
- The anterior surface of the forearm is usually less hairy than the posterior surface.
- The flexor muscles of the forearm are more massive than the extensors because they work against gravity.
- The main superficial veins of the forearm are the cephalic, median antebrachial, and basilic veins.
Frequently Asked Questions
What bones make up the forearm?
The forearm is built around two long bones: the radius on the thumb side and the ulna on the pinky side. Together they span the segment of the upper limb between the elbow and the wrist.
How is the forearm divided into compartments?
Fascial sheets split the forearm into an anterior compartment that houses the wrist and finger flexors and a posterior compartment containing the extensors. This separation keeps the two opposing muscle groups organized and allows them to work independently.
Which nerves run through the forearm?
Three major nerves — the median, radial, and ulnar — travel through the forearm to supply its muscles and skin. Each follows a distinct path, producing the region's characteristic pattern of sensation and motor control.
What joints does the forearm participate in?
The forearm connects to the rest of the limb via the elbow joint proximally and the wrist joint distally. It also forms proximal and distal radioulnar joints that permit the rotation needed for pronation and supination.
What is the vascular supply of the forearm?
The radial and ulnar arteries carry arterial blood through the forearm and anastomose to form the palmar arches near the wrist. Venous return is handled primarily by the cephalic, median antebrachial, and basilic veins.
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