2.3. Muscles

Hand movements are controlled by long muscles from the forearm and intrinsic muscles of the hand. The muscles found in the forearm can be divided into the flexor compartment (Figure 7.2 and Table 7.1), the lateral compartment (Table 7.2) and the extensor compartment of the forearm (Figure 7.3). These muscles exert their effect their effect via a series of tendons that pass into the wrist. The smaller intrinsic muscles of the hand are important for fine motor control (Figures 7.5, 7.6 and Table 7.4).

Table 7.1. Muscles of the flexor compartment of the forearm.

CompartmentMuscleOriginInsertionAction
SuperficialPronator teresMedial epicondyle of humerusLateral mid-shaft radiusPronation
Flexor carpi radialisMedial epicondyle of humerusBase of metacarpal bonesWrist flexion and abduction
Palmaris longusMedial epicondyle of humerusPalmer aponeurosisWrist flexion
Flexor carpi ulnarisOlecranon process of ulna and medial epicondyle of humerusPisiform boneWrist flexion and adduction
IntermediateFlexor digitorum superficialisMedial epicondyle of humerus, coranoid process of ulna and shaft of radiusGives rise to four tendons that pass under the flexor retinaculum, each split in two and inserted into the sides of each middle phalynxProximal IPJ flexion
DeepFlexor digitorum profundusAnterior and medial surface of ulna and interosseous membraneDistal phalynx of each fingerDistal IPJ flexion of fingers
Flexor pollicis longusAnterior surface of radius and interosseous membraneBase of distal phalynx of thumbIPJ flexion of thumb
Pronator quadratusLinear ridge of anterior ulnaDistal anterior radiusPronation

IPJ = interphalangeal joint.
Sources: Drake and Mitchell (2005) and Nakhdjevani and Ahmadi (2007).

Table 7.2. Muscles of the lateral compartment of the forearm.

CompartmentMuscleOriginInsertionAction
LateralBrachioradialisSupracondylar ridge of humerusStyloid process of radiusElbow flexion, pronation
Extensor carpi radialis longusSupracondylar ridge of humerusSecond metacarpal baseWrist extension and abduction

Sources: Drake and Mitchell (2005) and Nakhdjevani and Ahmadi (2007).

Table 7.3. Muscles of the extensor compartment of the forearm.

CompartmentMuscleOriginInsertionAction
SuperficialExtensor digitorumLateral epicondyle of humerusDivides into four tendons, that insert via ‘extensor hoods’ into dorsal base of middle and distal phalanges of fingersFinger extension
Extensor carpi radialis brevisLateral epicondyle of humerusThird metacarpal baseWrist extension and abduction
Extensor digiti minimiLateral epicondyle of humerusDorsal hood little fingerLittle finger MCPJ extension
Extensor carpi ulnarisLateral epicondyle of humerusPosterior base of fifth metacarpalWrist extension and adduction
DeepSupinatorLateral epicondyle of humerusNeck and shaft of radiusSupination
Abductor pollicis longusPosterior surface of radius and ulnaBase of first metacarpalThumb abduction and extension
Extensor pollicis brevisPosterior surface of radius and ulnaProximal phalanx of thumb baseMCPJ thumb extension
Extensor pollicis longusPosterior surface of radius and ulnaDistal phalanx of thumb baseIPJ thumb extension

IPJ = interphalangeal joint; MCPJ = metacarpophalangeal joint.
Sources: Drake and Mitchell (2005) and Nakhdjevani and Ahmadi (2007).

Table 7.4. Small muscles of the hand.

CompartmentMuscleOriginInsertionAction
HandLumbricalsTendons of FDPLateral side of extensor expansionMCPJ flexion and IPJ extension
InterosseiPalmar interosseiMedial side of metacarpalsExtensor hoods of thumb, index ring and little fingers and proximal phalanx of thumbAdduction of fingers
Dorsal interosseiSides of metacarpalsExtensor hoods and base of proximal phalanges of index, middle and ringAbduction index, middle and ring fingers
ThumbAbductor pollicis brevisScaphoid, trapezium and flexor retinaculumProximal phalanx and extensor hood of thumbThumb abduction
Flexor pollicis brevisTubercle of trapeziumProximal phalynx of thumbMCPJ thumb flexion
Opponens pollicisTrapezium and flexor retinaculumFirst metacarpalThumb medial rotation
Adductor pollicisBase of second and third metacarpalsMedial side or base of proximal phalanx of thumbThumb adduction
Little fingerAbductor digiti minimiPisiformProximal phalanx base of little fingerLittle finger abduction
Flexor digiti minimiFlexor retinaculumProximal phalanx base of little fingerLittle finger MCPJ flexion
Opponens digiti minimiFlexor retinaculumFifth metacarpal boneLaterally rotates metacarpal 5

FDP = flexor digitorum profundus; IPJ = interphalangeal joint; MCPJ = metacarpophalangeal joint.
Sources: Drake and Mitchell (2005) and Nakhdjevani and Ahmadi (2007).