What is considered your forearm? A comprehensive guide

October 2, 2025 •

3 min read

According to anatomical convention, the term 'arm' refers specifically to the part of the upper limb from the shoulder to the elbow. The section from the elbow to the wrist is known as the forearm, a complex region containing two major bones and a large network of muscles responsible for hand and wrist movement. Understanding what is considered your forearm is essential for comprehending its functions and overall health.

Quick Summary

The forearm is the region of the human arm located between the elbow and the wrist, consisting of the radius and ulna bones, along with numerous muscles, nerves, and blood vessels that enable crucial movements like gripping and rotation.

Key Points

Anatomical Boundaries: The forearm is the portion of the upper limb extending from the elbow joint down to the wrist joint.
Two Primary Bones: It is structured around two parallel bones, the radius (thumb side) and the ulna (pinky side), connected by the interosseous membrane.
Muscle Compartments: The forearm contains twenty muscles divided into anterior (flexor) and posterior (extensor) compartments, which control hand, wrist, and finger movements.
Key Functions: The forearm is responsible for complex movements like flexion, extension, pronation (palm down), and supination (palm up).
Vulnerability to Injury: It is a common site for fractures, repetitive strain injuries (RSIs), and other conditions due to its constant use in daily activities.

Demystifying the Anatomy: Defining the Forearm

The forearm, or antebrachium in anatomical terms, is a vital part of the upper body that facilitates many of our daily activities. It is a highly integrated structure, containing two long bones, the radius and the ulna, which are connected by a strong fibrous sheet called the interosseous membrane. This membrane and the bones divide the forearm into distinct compartments, each with specialized functions.

The Bony Framework of the Forearm

The forearm's stability and flexibility depend on its two primary bones working in concert. The radius is located on the lateral, or thumb side, of the forearm. Its structure allows it to pivot around the ulna, enabling the twisting movements of pronation (palm down) and supination (palm up). The ulna, positioned on the medial, or pinky side, is the larger and longer of the two bones and provides crucial stability to the elbow joint.

The Radius vs. The Ulna: A Comparison


Feature	Radius	Ulna
Location	Lateral side (thumb side)	Medial side (pinky side)
Length	Shorter of the two bones	Longer of the two bones
Elbow Articulation	Articulates with the humerus and ulna	Articulates with the humerus and radius
Wrist Articulation	Forms the majority of the wrist joint	Articulates with the radius, but not directly with most wrist bones
Primary Function	Pivots around the ulna to enable rotation	Provides stability to the forearm

Muscular Compartments of the Forearm

Within the forearm, muscles are organized into two main compartments separated by the interosseous membrane.

Anterior (Flexor) Compartment: Located on the palm side of the forearm, this compartment contains muscles responsible for flexing the wrist and fingers and pronating the forearm. It is further divided into superficial, intermediate, and deep layers.

Superficial Layer: Includes the pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris.
Intermediate Layer: Primarily consists of the flexor digitorum superficialis.
Deep Layer: Contains the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus.

Posterior (Extensor) Compartment: On the back of the forearm, these muscles are involved in extending the wrist and fingers, as well as supinating the forearm. This compartment has superficial and deep layers.

Superficial Layer: Includes the brachioradialis, extensor carpi radialis longus and brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris.
Deep Layer: Contains the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.

Nerve and Blood Supply

Major nerves and blood vessels also run through the forearm, ensuring the muscles and tissues are properly supplied and functional. The median, ulnar, and radial nerves provide innervation, with specific nerves controlling different muscle groups. The radial and ulnar arteries carry blood to the forearm and hand.

Common Forearm Health Issues and Injuries

Given its complexity and constant use, the forearm is susceptible to various injuries and conditions. These can range from minor strains to more serious fractures.

Fractures: Breaks in the radius, ulna, or both are common, often resulting from falls onto an outstretched hand or a direct blow.
Repetitive Strain Injuries (RSIs): Conditions like carpal tunnel syndrome, tennis elbow (lateral epicondylitis), and golfer's elbow (medial epicondylitis) are caused by repetitive motions that stress the forearm muscles and tendons.
Compartment Syndrome: A serious condition where swelling within the muscle compartments causes dangerous pressure buildup, potentially leading to nerve and muscle damage.
Tendonitis: Inflammation of a tendon, a common issue for athletes and individuals performing repetitive tasks.

The Importance of Forearm Strength and Health

Strong, healthy forearms are crucial for more than just lifting weights. They are fundamental for grip strength, wrist stability, and performing everyday tasks like opening jars, writing, and carrying groceries. Incorporating targeted forearm exercises, such as wrist curls and farmer's walks, can improve your grip and support the health of your joints and surrounding muscles.

Conclusion

The forearm is the anatomical region between your elbow and your wrist, and it is a marvel of biological engineering. With its intricate arrangement of two bones, twenty muscles, and a comprehensive neurovascular network, it provides the strength, stability, and dexterity needed for the hand and fingers to function. By understanding what is considered your forearm and how it works, you can better appreciate its importance and take proactive steps to maintain its health and strength.

For more in-depth anatomical resources, the National Library of Medicine offers detailed information on various body parts.

Frequently Asked Questions

In anatomical terms, the 'arm' refers specifically to the upper arm, from the shoulder to the elbow. The 'forearm' is the lower part of the limb, from the elbow to the wrist.

The forearm contains two long bones: the radius, located on the thumb side, and the ulna, situated on the pinky side. The radius and ulna articulate with each other and with the humerus and wrist bones.

The muscles of the forearm control the movements of the hand, wrist, and fingers. The anterior muscles primarily flex and pronate, while the posterior muscles extend and supinate.

Common forearm injuries include fractures of the radius or ulna, repetitive strain injuries like tennis elbow or carpal tunnel syndrome, and tendonitis from overuse.

You can strengthen your forearms with exercises that target both the flexor and extensor muscles, including wrist curls (palm up and down), hammer curls, and grip exercises like farmer's carries.

Yes, strengthening your forearm muscles directly improves your grip strength. Many forearm muscles are responsible for controlling the fingers and thumbs used for gripping objects.

You can easily remember the difference by their location relative to your thumb and pinky. The radius is always on the thumb side (radial side), while the ulna is on the pinky side (ulnar side).