The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm. It is

homologous Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor *Sequence homology, biological homology between DNA, RNA, or protein sequences * Homologous chrom ...

to the region of the leg that lies between the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

and the ankle joints, the

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. The forearm contains two long bones, the radius and the ulna, forming the two radioulnar joints. The interosseous membrane connects these bones. Ultimately, the forearm is covered by skin, the anterior surface usually being less hairy than the posterior surface. The forearm contains many muscles, including the flexors and extensors of the wrist, flexors and extensors of the digits, a flexor of the elbow ( brachioradialis), and

pronator Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

s and

supinator In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm. Structure Supinator consists of two planes of fibers, between whi ...

s that turn the hand to face down or upwards, respectively. In cross-section, the forearm can be divided into two fascial compartments. The posterior compartment contains the extensors of the hands, which are supplied by the

radial nerve The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial comp ...

. The anterior compartment contains the flexors and is mainly supplied by the median nerve. The flexor muscles are more massive than the extensors because they work against gravity and act as anti-gravity muscles. The

ulnar nerve In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...

also runs the length of the forearm. The radial and ulnar arteries and their branches supply the blood to the forearm. These usually run on the anterior face of the radius and ulna down the whole forearm. The main superficial veins of the forearm are the cephalic, median antebrachial and the basilic vein. These veins can be used for cannularisation or venipuncture, although the cubital fossa is a preferred site for getting blood.

Structure

Bones and joints

The bones of the forearm are the radius (located on the lateral side) and the ulna (located on the medial side) Radius and Ulna - Forearm Bones

Radius

Proximally, the head of the radius articulates with the capitulum of the humerus and the radial notch of the ulna at the elbow. The articulation between the radius and the ulna at the elbow is known as the proximal radioulnar joint. Distally, it articulates with the ulna again at the

distal radioulnar joint The distal radioulnar articulation (also known as the distal radioulnar joint, or inferior radioulnar joint) is a synovial pivot joint between the two bones in the forearm; the radius and ulna. It is one of two joints between the radius and ulna, ...

. It forms part of the wrist joint by articulating with the scaphoid at its lateral aspect and with the lunate at its medial aspect.

Ulna

Proximally, the

trochlear notch The trochlear notch (), also known as semilunar notch and greater sigmoid cavity, is a large depression in the upper extremity of the ulna that fits the trochlea of the humerus (the bone directly above the ulna in the arm) as part of the elbow jo ...

of the ulna articulates with the trochlea of the humerus and the radial notch articulates with the head of the radius at the elbow. Distally it forms part of the

and also articulates with the wrist.

Muscles

* "E/I" refers to "extrinsic" or "intrinsic". The intrinsic muscles of the forearm act on the forearm, meaning, across the elbow joint and the

proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...

and

distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

radioulnar joints (resulting in

pronation Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

, whereas the extrinsic muscles act upon the hand and wrist. In most cases, the extrinsic anterior muscles are ''flexors'', while the extrinsic posterior muscles are ''extensors''. * The brachioradialis, flexor of the forearm, is unusual in that it is located in the posterior compartment, but it is actually in the anterior portion of the forearm. * The anconeus is considered by some as a part of the posterior compartment of the arm.

Nerves

:''See separate nerve articles for details on divisions proximal to the elbow and distal to the wrist; see Brachial plexus for the origins of the median, radial and ulnar nerves.'' * Median nerve – interior nerve of the anterior compartment ( PT,

FCR FCR may refer to: Science and medicine * Fc receptor * Fire-cracked rock * Flexor carpi radialis muscle * Folin–Ciocalteu reagent *Fuji computed radiography, name of a series of computed radiography systems made by Fujifilm Sport * FCR 2001 ...

, PL, FDS). ** anterior interosseous nerve (supplies FPL, lat. 1/2 of FDP, PQ). *

Radial nerve The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial comp ...

– supplies muscles of the posterior compartment ( ECRL,

ECRB In human anatomy, extensor carpi radialis brevis is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the exten ...

). ** Superficial branch of radial nerve ** Deep branch of radial nerve, becomes

Posterior interosseus nerve The posterior interosseous nerve (or dorsal interosseous nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared t ...

and supplies muscles of the posterior compartment ( ED,

EDM EDM or E-DM may refer to: Music * Electronic dance music * Early Day Miners, American band Science and technology * Electric dipole moment * Electrical discharge machining * Electronic distance measurement *Entry, Descent, and landing demonstra ...

, ECU, APL,

EPB EPB of Chattanooga, formerly known as the Electric Power Board of Chattanooga, is an American electric power distribution and telecommunications company owned by the city of Chattanooga, Tennessee. EPB serves nearly 180,000 homes and businesses ...

, EPL, EI). *

Ulnar nerve In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...

– supplies some medial muscles ( FCU, med. 1/2 of FDP).

Vessels

Brachial artery The brachial artery is the major blood vessel of the (upper) arm. It is the continuation of the axillary artery beyond the lower margin of teres major muscle. It continues down the ventral surface of the arm until it reaches the cubital fossa ...

** Radial artery *** Radial recurrent artery ***

dorsal metacarpal artery The dorsal carpal arch (dorsal carpal network, posterior carpal arch) is an anatomical term for the combination (anastomosis) of dorsal carpal branch of the radial artery and the dorsal carpal branch of the ulnar artery near the back of the wrist. ...

**** Princeps pollicis artery ** Ulnar artery *** Anterior ulnar recurrent artery and posterior ulnar recurrent artery *** Common interosseous artery ****

Posterior interosseous artery The posterior interosseous artery (dorsal interosseous artery) is an artery of the forearm. It is a branch of the common interosseous artery, which is a branch of the ulnar artery. Structure The posterior interosseous artery passes backward betw ...

****

Anterior interosseous artery The anterior interosseous artery (volar interosseous artery) is an artery in the forearm. It is a branch of the common interosseous artery. Course It passes down the forearm on the palmar surface of the interosseous membrane. It is accompanied ...

Other structures

* Interosseous membrane of forearm * Annular ligament of ulna

Function

The forearm can be brought closer to the upper arm ( flexed) and brought away from the upper arm (

extended Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Exte ...

) due to movement at the elbow. The forearm can also be rotated so that the palm of the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...

rotates inwards ( pronated) and rotated back so that the palm rotates outwards (

supinated Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

) due to movement at the elbow and the

Clinical significance

fracture Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...

of the forearm can be classified as to whether it involves only the ulna (

ulnar fracture The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in Standard anatomical position, anatomical position, is found on the Medial (anatomy), medial side of the forear ...

), only the radius ( radius fracture), or both radioulnar fracture. For treatment of children with torus fractures of the forearm splinting appears to work better than casting. Genetically determined disorders like hereditary multiple exostoses can lead to hand and forearm deformities. Hereditary multiple exostoses is due growth disturbance of the epiphyses of the radius and ulna, the two bones of the forearm.

Additional images

References

{{Authority control Upper limb anatomy