Anatomy Muscle Actions: Spine, Hip, Leg, and Foot

Semispinalis capitis

Acting together, extend head and vertebral column; acting singly, rotate head to side opposite contracting muscle.

Semispinalis colli

Acting together, both semispinalis cervicis and both semispinalis thoracis muscles extend vertebral column of their respective regions; acting singly, rotate head to side opposite contracting muscle.

Semispinalis thoracis

Acting together, both semispinalis cervicis and both semispinalis thoracis muscles extend vertebral column of their respective regions; acting singly, rotate head to side opposite contracting muscle.

Multifidus

Acting together, extend vertebral column; acting singly, weakly laterally flex vertebral column and weakly rotate vertebral column to side opposite contracting muscle.

Rotatores

Acting together, weakly extend vertebral column; acting singly, weakly rotate vertebral column to side opposite contracting muscle.

Interspinales

Acting together, weakly extend vertebral column; acting singly, stabilize vertebral column during movement.

Intertransversarii

Acting together, weakly extend vertebral column; acting singly, weakly laterally flex vertebral column and stabilize it during movements.

Scalenus anterior

Acting together, right and left scalenus anterior and scalenus medius muscles elevate first ribs during deep inhalation.

Scalenus medius

RMA: Flex cervical vertebrae; acting singly, laterally flex and slightly rotate cervical vertebrae.

Scalenus posterior

Acting together, right and left scalenus posterior elevate second ribs during deep inhalation. RMA: Flex cervical vertebrae; acting singly, laterally flex and slightly rotate cervical vertebrae.

Psoas major

Psoas major and iliacus muscles acting together flex thigh at hip joint, rotate thigh laterally, and flex trunk on hip as in sitting up from supine position.

Iliacus

Psoas major and iliacus muscles acting together flex thigh at hip joint, rotate thigh laterally, and flex trunk on hip as in sitting up from supine position.

Gluteus maximus

Extends and laterally rotates hip joint.

Gluteus medius

Abducts and medially rotates hip joint.

Gluteus minimus

Abducts and medially rotates hip joint.

Tensor fasciae latae

Flexes and abducts hip joint.

Piriformis

Laterally rotates and abducts hip joint.

Obturator internus

Laterally rotates and abducts hip joint.

Obturator externus

Laterally rotates and abducts hip joint.

Superior gemellus

Laterally rotates and abducts hip joint.

Inferior gemellus

Laterally rotates and abducts hip joint.

Quadratus femoris

Laterally rotates and stabilizes hip joint.

Adductor longus

Adducts and flexes thigh at hip joint and rotates thigh.*

Adductor brevis

Adducts and flexes thigh at hip joint and rotates thigh.*

Adductor magnus

Adducts thigh at hip joint and rotates thigh; anterior part flexes thigh at hip joint, and posterior part extends thigh at hip joint.*

Pectineus

Flexes and adducts thigh at hip joint.

Sartorius

Weakly flexes leg at knee joint; weakly flexes, abducts, and laterally rotates thigh at hip joint.

Biceps femoris

Extends thigh at hip joint.

Semitendinosus

Extends thigh at hip joint.

Semimembranosus

Flexes leg at knee joint and extends thigh at hip joint.

Tibialis anterior

Dorsiflexes foot at ankle joint and inverts (supinates) foot at intertarsal joints.

Extensor hallucis longus

Dorsiflexes foot at ankle joint and extends proximal phalanx of great toe at metatarsophalangeal joint.

Extensor digitorum longus

Dorsiflexes foot at ankle joint and extends distal and middle phalanges of each toe at interphalangeal joints and proximal phalanx of each toe at metatarsophalangeal joint.

Fibularis (peroneus) tertius

Dorsiflexes foot at ankle joint and everts (pronates) foot at intertarsal joints.

Fibularis (peroneus) longus

Plantar flexes foot at ankle joint and everts (pronates) foot at intertarsal joints.

Fibularis (peroneus) brevis

Plantar flexes foot at ankle joint and everts (pronates) foot at intertarsal joints.

Gastrocnemius

Plantar flexes foot at ankle joint and flexes leg at knee joint.

Soleus

Plantar flexes foot at ankle joint.

Plantaris

Plantar flexes foot at ankle joint and flexes leg at knee joint.

Popliteus

Flexes leg at knee joint and medially rotates tibia to unlock the extended knee.

Tibialis posterior

Plantar flexes foot at ankle joint and inverts (supinates) foot at intertarsal joints.

Flexor digitorum longus

Plantar flexes foot at ankle joint; flexes distal and middle phalanges of toes 2-5 at interphalangeal joints and proximal phalanx of toes 2-5 at metatarsophalangeal joint.

Flexor hallucis longus

Plantar flexes foot at ankle joint; flexes distal phalanx of great toe at interphalangeal joint and proximal phalanx of great toe at metatarsophalangeal joint.

Extensor hallucis brevis

Extends great toe at metatarsophalangeal joint.

Extensor digitorum brevis

Extends toes 2-4 at interphalangeal joints.

Abductor hallucis

Abducts and flexes great toe at metatarsophalangeal joint.

Flexor digitorum brevis

Flexes toes 2-5 at proximal interphalangeal and metatarsophalangeal joints.

Abductor digiti minimi

Abducts and flexes little toe at metatarsophalangeal joint.

Quadratus plantae

Assists flexor digitorum longus to flex only toes 2-5 at interphalangeal and metatarsophalangeal joints.

Lumbricals

Extend toes 2-5 at interphalangeal joints and flex toes 2-5 at metatarsophalangeal joints.

Flexor hallucis brevis

Flexes great toe at metatarsophalangeal joint.

Adductor hallucis

Adducts and flexes great toe at metatarsophalangeal joint.

Flexor digiti minimi brevis

Flexes little toe at metatarsophalangeal joint.

Dorsal interossei

Abduct and flex toes 2-4 at metatarsophalangeal joints and extend toes at interphalangeal joints.

Plantar interossei

Adduct and flex proximal metatarsophalangeal joints and extend toes at interphalangeal joints.

Levator ani

Muscle is divisible into three parts: pubococcygeus muscle, puborectalis muscle, and iliococcygeus muscle.

Pubococcygeus

Supports and maintains position of pelvic viscera; resists increase in intra-abdominal pressure during forced exhalation, coughing, vomiting, urination, and defecation; constricts anus, urethra, and vagina.

Puborectalis

Helps maintain fecal continence and assists in defecation.

Iliococcygeus

Same as pubococcygeus

Ischiococcygeus

Supports and maintains position of pelvic viscera; resists increase in intra-abdominal pressure during forced exhalation, coughing, vomiting, urination, and defecation; pulls coccyx anteriorly following defecation or childbirth.

Superficial transverse perineal

Stabilizes perineal body of perineum.

Bulbospongiosus

Helps expel urine during urination, helps propel semen along urethra, assists in erection of penis in male; constricts vaginal orifice and assists in erection of clitoris in female.

Ischiocavernosus

Maintains erection of penis in male and clitoris in female by decreasing urine drainage.

Deep transverse perineal

Helps expel last drops of urine and semen in male.

External urethral sphincter

Helps expel last drops of urine and semen in male and urine in female.

Compressor urethrae

Serves as accessory sphincter of urethra.

Sphincter urethrovaginalis

Serves as accessory sphincter of urethra and facilitates closing of vagina.

External anal sphincter

Keeps anal canal and anus closed.

Subclavius

Depresses and moves clavicle anteriorly and helps stabilize pectoral girdle.

Pectoralis minor

Abducts scapula and rotates it downward. RMA: Elevates ribs 3-5 during forced inhalation when scapula is fixed.

Serratus anterior

Abducts scapula and rotates it upward. RMA: Elevates ribs when scapula is stabilized. Known as "boxer's muscle" because it is important in horizontal arm movements such as punching and pushing.

Trapezius

Superior fibers upward rotate scapula; middle fibers adduct scapula; inferior fibers depress and upward rotate scapula; superior and inferior fibers together rotate scapula upward; stabilizes scapula. RMA: Superior fibers can help extend head.

Levator scapulae

Elevates scapula and rotates it downward; laterally flexes neck to same side.

Rhomboid major

Adducts scapula and rotates it downward; stabilizes scapula.

Rhomboid minor

Adducts scapula and rotates it downward; stabilizes scapula.

Pectoralis major

As a whole, adducts and medially rotates arm at shoulder joint; clavicular head flexes arm, and sternocostal head flexes the extended arm to side of trunk.

Latissimus dorsi

Extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly. RMA: Elevates vertebral column and torso.

Deltoid

Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder joint.

Subscapularis

Medially rotates arm at shoulder joint.

Supraspinatus

Assists deltoid muscle in abducting arm at shoulder joint.

Infraspinatus

Laterally rotates arm at shoulder joint.

Teres major

Extends arm at shoulder joint and assists in adduction and medial rotation of arm at shoulder joint.

Teres minor

Laterally rotates and extends arm at shoulder joint.

Coracobrachialis

Flexes and adducts arm at shoulder joint.

Biceps brachii

Flexes forearm at elbow joint, supinates forearm at radioulnar joints, and flexes arm at shoulder joint.

Brachialis

Flexes forearm at elbow joint.

Brachioradialis

Flexes forearm at elbow joint most effectively when arm is mid-pronated.

Triceps brachii

Extends forearm at elbow joint and extends arm at shoulder joint.

Anconeus

Extends forearm at elbow joint.

Pronator teres

Pronates forearm at radioulnar joints and weakly flexes forearm at elbow joint.

Pronator quadratus

Pronates forearm at radioulnar joints.

Supinator

Supinates forearm at radioulnar joints.

Flexor carpi radialis

Flexes and abducts hand (radial deviation) at wrist joint.

Palmaris longus

Weakly flexes hand at wrist joint.

Flexor carpi ulnaris

Flexes and adducts hand (ulnar deviation) at wrist joint.

Flexor digitorum superficialis

Flexes middle phalanx of each finger at proximal interphalangeal joint, proximal phalanx of each finger at metacarpophalangeal joint, and hand at wrist joint.

Flexor pollicis longus

Flexes distal phalanx of thumb at interphalangeal joint.

Flexor digitorum profundus

Flexes distal and middle phalanges of each finger at interphalangeal joints, proximal phalanx of each finger at metacarpophalangeal joint, and hand at wrist joint.

Extensor carpi radialis longus

Extends and abducts hand at wrist joint (ulnar deviation).

Extensor carpi radialis brevis

Extends and abducts hand at wrist joint.