Comprehensive Guide to Forearm Anatomy: Parts, Names, Functions & Diagram

The forearm, situated between the elbow and the wrist in the upper limb, possesses an intriguing charm. From an anatomical perspective, the term “forearm” gracefully distinguishes itself from the broader descriptor of the “arm,” which specifically refers to the upper arm. Therefore, the precise anatomy of a forearm proudly claims its domain in the lower limb. Drawing a stunning parallel, we can observe a homologous counterpart to the knee-to-ankle span in the leg known as the crus, highlighting the harmonious design of nature. The forearm anatomy consists of two long bones, namely the radius and ulna, running parallel to each other. Set on the lateral side, the radius, and the medial side host the ulna. These bones offer structural support and enable various forearm movements, including pronation and supination.

Forearm Anatomy

Forearm Anatomy, Parts, Names & Diagram

Parts of a Forearm


  • Flexor Muscles
    • Flexor Digitorum Profundus
    • Flexor Digitorum Superficialis
    • Flexor Carpi Ulnaris
    • Flexor Carpi Radialis
  • Extensor Muscles
    • Extensor Carpi Radialis Longus
    • Extensor Carpi Radialis Brevis
    • Extensor Digitorum
    • Extensor Carpi Ulnaris
  • Pronator Muscles
    • Pronator Teres
    • Pronator Quadratus
  • Supinator Muscle
  • Other Muscles
    • Brachioradialis
    • Anconeus
    • Palmaris Longus
    • Extensor Indicis


  • Ulna
  • Radius


  • Elbow Joint
  • Radioulnar Joints


  • Median Nerve
  • Radial Nerve
  • Ulnar Nerve

Blood Vessels

  • Brachial Artery
  • Ulnar Artery
  • Radial Artery

Forearm Anatomy: Parts & Functions

Unveil the captivating marvels hidden within the depths of your forearm. This mysterious world between your elbow’s exquisite bend and your wrist’s deft sweep reveals a kaleidoscope. Fascinating bones, joints, muscles, complex tendons, and lively nerves.

Forearm Muscle Anatomy

Flexor Muscles

The flexor muscles of the forearm are impressive powerhouses. They enable us to perform astonishing feats of skill and strength. These muscles are located on the anterior side of the forearm. They possess a remarkable ability to flex or bend the wrist, fingers, and thumb. They do so with astonishing precision.

  1. Flexor Digitorum Profundus

The flexor digitorum profundus muscle dominates the inner landscape of the forearm. Its tendons, resembling sturdy ropes, effortlessly maneuver through the intricate pulley system within the hand, finally attaching to the distal phalanges.

This mighty muscle flexes the distal interphalangeal joints, enabling us to curl our fingers with enviable control.

  1. Flexor Digitorum Superficialis

The flexor digitorum superficialis muscle orchestrates the movement of our fingers with finesse. This muscle pulls the strings on the proximal and middle phalanges, gracefully folding them in unison.

It is crucial in delicate tasks requiring precise finger coordination. Examples include playing a musical instrument or engaging in intricate craftsmanship.

  1. Flexor Carpi Ulnaris

Nestled on the ulnar side of the forearm, the flexor carpi ulnaris muscle boasts an impressive strength that would rival a titan’s grip. Its sinewy fibers tirelessly contract, bending the wrist towards the ulnar (little finger) side.

This muscle becomes a formidable ally in tasks that demand a firm grip or forceful hand movements. It is especially useful when wielding a hammer or lifting heavy objects.

  1. Flexor Carpi Radialis

The flexor carpi radialis muscle resides on the forearm’s radial (thumb) side, akin to a steadfast sentinel.

Its strong contractions flex the wrist towards the radial side. This ability is invaluable in wielding a paintbrush or swiftly maneuvering a steering wheel.

Extensor Muscles

The extensor muscles of the forearm exhibit remarkable prowess. They counteract the flexors and allow us to elegantly extend and straighten our wrists, fingers, and thumbs. These dynamic muscles reside on the posterior side of the forearm, ready to spring into action at a moment’s notice.

  1. Extensor Carpi Radialis Longus

The extensor carpi radialis longus muscle emerges as a beacon of strength on the outer landscape of the forearm. It flexes its sinewy might, extending the wrist with unwavering determination. This forceful movement proves invaluable in executing a powerful backhand swing in tennis or wielding a sword in battle.

  1. Extensor Carpi Radialis Brevis

The extensor carpi radialis brevis muscle adds strength to the symphony of extension in the forearm. This muscle ensures that the wrist extends precisely, enabling us to reach for the stars or grasp objects with finesse.

  1. Extensor Digitorum

The extensor digitorum muscle fibers radiate outwards, extending across the expanse of the hand, where they terminate in delicate tendons.

This muscle orchestrates the extension of our fingers. It allows us to unfold them with effortless ease after flexing.

4. Extensor Carpi Ulnaris

The ulnar side of the forearm, the extensor carpi ulnaris muscle, embodies resilience and stability. Its unwavering contractions can extend the wrist towards the ulnar side. It facilitates actions like stretching the hand or executing a graceful wrist flick.

Pronator Muscles

The pronator muscles unveil their special role in the rotational movement in forearm biology. With their intrinsic ability to pronate the forearm and turn the palm downward or posteriorly, these muscles provide a unique dimension to the forearm’s biomechanical symphony.

  1. Pronator Teres

The pronator teres muscle exhibits an excellent command over forearm pronation. A conductor guides an orchestra. This muscle orchestrates the rotation of the forearm with impressive finesse. It simultaneously turns the palm downward and flexes the elbow.

  1. Pronator Quadratus

Deep within the layers of the forearm, the pronator quadratus muscle assumes the role of a steadfast stabilizer and a precision engineer. With meticulous attention to detail, it fine-tunes the pronation movement, ensuring the forearm rotates smoothly and effortlessly.

This mighty muscle safeguards against undesirable wrist movements, granting us the gift of precision in our daily endeavors.

Supinator Muscle

The supinator muscle is a powerful counterbalance to the pronators. It skillfully bestows us with the ability to supinate the forearm and turn the palm upwards or anteriorly. This remarkable muscle resides on the outer side of the forearm, akin to a guardian of supination.

Supinator: Unleashing its might with awe-inspiring elegance, the supinator muscle showcases its supremacy over supination. The supinator muscle springs into action when the need arises to turn the palm upwards or perform tasks such as using a screwdriver or opening a jar. It performs its role with effortless grace. Its commanding contractions effortlessly bring the palm to a victorious upward position.

Other Muscles

A cast of supporting characters adds depth and complexity. They contribute to the saga of muscle interplay and functionality.

  1. Brachioradialis

The brachioradialis muscle serves as an agile accomplice in forearm movement. Its versatile nature enables it to contribute to flexion and extension of the forearm, adjusting its efforts based on the task. This muscle adapts when lifting a heavy object or delicately manipulating fine tools.

  1. Anconeus

The anconeus muscle emerges, bestowing stability and finesse to the region. Its unwavering dedication to extending the forearm and stabilizing the elbow joint ensures smooth and controlled movements. It protects against unwanted stress or strain.

  1. Palmaris Longus

The palmaris longus muscle adds a touch of uniqueness to the forearm landscape. While absent in some individuals, its presence brings forth an intriguing dynamic. This muscle flexes the wrist and tenses the palmar fascia, contributing to the intricate ballet of hand movements.

  1. Extensor Indicis

The extensor indicis muscle assumes a vital role in extending the index finger. A conductor guides a soloist. It ensures that the index finger performs its role precisely. It enables us to point, grasp, or execute refined gestures accurately.



The ulna is the longer and more robust of the two forearm bones. The ulna dominates the medial border of the forearm, extending from the elbow to the wrist. A thin bone called the ulna connects the radius, its brother, at the elbow.

Comprising shaft, proximal, and distal ends. It forges an unbreakable bond with the humerus at the elbow joint. It also forges an unbreakable bond with the radius at the wrist joint.

Mighty and relentless, the ulna serves as a stalwart support system for the forearm. Seamlessly collaborating with the humerus and radius, it ensures stability and endows the forearm with unwavering strength.

Furthermore, the ulna unleashes its power in forearm rotation. It enables the hand to pivot effortlessly between supination (palm-up) and pronation (palm-down).

The ulna proudly hosts muscle attachments as a testament to its indomitable nature. These attachments orchestrate precise movements and enhance grip strength.


This captivating bone claims its rightful place on the outer side of the forearm, running parallel to the ulna.

The radius extends from the elbow to the wrist, mirroring the ulna’s length. This bone has a strong shaft. It also has proximal and distal ends, which join forces with the humerus at the elbow joint. It also joins forces with the ulna and the scaphoid bone at the wrist joint.

Fearlessly venturing into uncharted territories, the radius takes command of forearm rotation. Its audacious movement around the ulna allows the hand to transition seamlessly. It transitions from a palm-down (pronated) position to a palm-up (supinated) position. It also transitions and vice versa.

This courageous act of rotation empowers us to pour liquids, turn doorknobs, and skillfully wield tools. In addition, the radius fortifies the stability of the wrist joint. It provides sturdy anchor points for the muscles orchestrating the mesmerizing forearm and hand movements symphony.


Elbow Joint

The elbow joint is nestled within the forearms. These grant it unparalleled versatility and finesse in orchestrating upper limb movements.

The captivating joint comprises an intricate interplay of skeletal structures, connective tissues, and muscular apparatus. It is a beautiful testament to the wonders of biological engineering.

The bones constituting the elbow joint exhibit a remarkably distinctive arrangement, comprising the humerus, radius, and ulna. Their intricate fusion establishes a foundation of stability while accommodating an exceptional range of motion.

Adjacent ligaments, such as the ulnar collateral ligament (UCL) and radial collateral ligament (RCL), exhibit intricately woven fibers. These fibers provide robust support and protect against excessive strain.

The surrounding musculature, a symphony of biological architecture, astounds with its intricate design and flawless coordination.

The biceps brachii, triceps brachii, brachialis, and brachioradialis harmoniously cooperate. They exhibit unparalleled strength and refined control. These muscles are involved in flexion, extension, pronation, and supination.

Radioulnar Joints

Starting with the proximal radioulnar joint near the elbow lies an astonishing elastic ligament known as the “radial spiral ligament.”

This specialized ligament not only encircles the head of the radius. It also exhibits an unparalleled ability to undergo intricate helical movements during pronation and supination. This biomechanical phenomenon allows for seamless rotation of the forearm with unparalleled precision.

Delving deeper into the distal radioulnar joint, an extraordinary component known as the “triradial cartilage complex” takes center stage. Unlike conventional cartilage structures, this unique complex possesses a three-dimensional arrangement of fibrocartilaginous tissues. These tissues mimic the intricate patterns observed in the natural world.

Its intricate collagen fibers and proteoglycans network provide exceptional stability and shock absorption during rotational movements, ensuring optimal joint function.

Combining these biologically powerful features in the radioulnar joints enables an astonishing array of movements. These movements extend beyond simple flexion and extension.


Median Nerve

The median nerve, a vital player in the forearm’s nerve network, embarks on a remarkable journey from the brachial plexus. This nerve showcases its versatility by controlling the wrist, fingers, and thumb flexion.

It paints a vibrant sensory canvas on the palmar side of the thumb, index finger, middle finger, and half of the ring finger. It lets us perceive the world through touch, temperature, and pain.

However, beware of the perils of carpal tunnel syndrome. It arises from the nerve’s compression, resulting in a symphony of numbness, tingling, and discomfort in the affected hand.

Radial Nerve

A courageous explorer among the nerves, the radial nerve forges its path from the mighty brachial plexus, tracing a course along the back of the forearm. Its audacious purpose?

To empower us to extend our elbow, wrist, and fingers, enabling feats of strength, reach, and skill. Sensory tales from this intrepid traveler involve the skin on the back of the hand. It also includes the dorsal frontier of the thumb. It also encompasses the ring finger’s index, middle, and half.

Ulnar Nerve

The ulnar nerve emerges gallantly from the brachial plexus, poised to bestow its gift of skill upon the hand. With meticulous precision, it orchestrates the symphony of delicate movements that allow us to pinch, grip, and maneuver objects with finesse.

This nerve reveals its sensory prowess by bestowing the gift of sensation upon the little finger, half of the ring finger, and their tender fingertips. Alas, be wary of the perils of ulnar neuropathy. It is a foe that may inflict tingling, numbness, and weakness upon the hand. Such symptoms threaten the harmony of these delicate movements.

Blood Vessels

Brachial Artery

Behold the brachial artery expedition through the upper arm’s rugged terrain. This life-giving conduit is born from the axillary artery and dares to traverse the treacherous path from shoulder to elbow. It is a relentless supplier of vitality to the arm’s muscular battalions. It also nourishes the resilient joint of the elbow.

We encounter the audacious deep brachial artery. It ventures into the hinterlands of the posterior arm to nourish and fortify the mighty muscle masses dwelling within.

This artery reveals its secrets when palpated in the arm’s hidden groove. It offers insights into the ever-flowing currents of blood pressure.

Ulnar Artery

The ulnar artery aligns with the ulna bone. It is a steadfast companion, sustaining the muscles, delicate skin, and intricate hand structures. It divides into the anterior and posterior interosseous arteries. These arteries delve deep into the forearm, nurturing the profound muscular realms.

The climax of this tale lies in the creation of the superficial and deep palmar arches. These arches grace the palm’s fertile grounds, bestowing vitality upon the fingers’ enchanting choreography.

Radial Artery

Prepare to be mesmerized by the radial artery, a veritable force of nature that reigns supreme along the thumb side of the forearm. This artery delivers life-sustaining resources to the muscles, wrist, and intricate hand landscapes.

The radial artery elegantly traverses the radius bone from the elbow to the wrist. It leaves an indelible mark on the anatomical tapestry. A real testament to its magnificence lies just below the base of the thumb. Its vibrant pulsations can be felt, reminiscent of nature’s rhythmic symphony.

Witness the crowning glory of the radial artery’s legacy as it bestows upon the palm the magnificent scaffolding of the superficial palmar arch. It fortifies the palm’s paradise and contributes to the ethereal orchestration of the hand’s wondrous capabilities.

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