Lower Limb/Back/Suboccipital Triangle Muscles

Psoas Major

Origin: sides of T12-L5 vertebrae and the discs between them; transverse processes of all lumbar vertebrae

Insertion: lesser trochanter of femur

Innervation: anterior rami of lumbar nerve (L1, L2, L3)

Action: acts conjointly with the iliacus to flex and stabalize the hip joint; postural muscle that helps control deviation of the trunk and is active during standing

Fibularis Tertius

Origin: inferior third of anterior surface of fibula and interosseous membrane

Insertion: dorsom of base of 5th metatarsal

Innervation: deep fibular nerve (L5, S1)

Action: dorsiflexes ankle; aids in eversion of foot

Gluteus Minimus

Origin: external surface of ilium between anterior and inferior gluteal lines

Insertion: anterior surface of greater trochanter of femur

Innervation: superior gluteal nerve (L4, L5, S1)

Action: abduct and anterior portions medially rotate hip joint; keep pelvis level when opposite limb is elevated

Obturator externus

Origin: margins of obturator foramen and obturator membrane

Insertion: trochanteric fossa of femur

Innervation: obturator nerve (L3, L4)

Action: laterally rotates hip joint; pulls head of femur into acetabulum holding pelvis steady

Adductor Brevis

Origin: body and inferior ramus of pubis

Insertion: pectineal line and proximal part of linea aspera of femur

Innervation: obturator line (L2, L3, L4)

Action: adducts hip joint and to some extent flexes it

Iliacus

Origin: iliac crest, iliac fossa, ala of sacrum, and anterior sacro-iliac ligaments

Insertion: tendon of psoas major, lesser trochanter of femur and distal to it

Innervation: femoral nerve (L2, L3)

Action: acts conjointly with psoas major to flex and stabilize the hip joint

Iliopsoas

psoas major and iliacus muscles combine to form this muscle as it enters the thigh region

Gluteus Maximus

Origin: ilium posterior to posterior gluteal line, dorsal surface of sacrum and coccyx; and sacrotuberous ligament

Insertion: most fibers end in iliotibial tract, which inserts into lateral condyle of tibia; some fibers insert on gluteal tuberosity of femur

Innervation: inferior gluteal nerve (L5, S1, S2)

Action: extends hip joint between flexed and standing positions and assists in its lateral rotation; steadies thigh and assists in rising from sitting position

Gluteus Medius

Origin: external surface of ilium between anterior and posterior gluteal lines

Insertion: lateral surface of greater trochanter of femur

Innervation: superior gluteal nerve (L4, L5, S1)

Action: abducts and anterior portions medially rotate hip joint; keeps pelvis level when opposite limb is elevated

Tensor Fascia Latae

Origin: anterior superior iliac spine; anterior part of iliac crest

Insertion: iliotibial tract, which attaches to lateral condyle of tibia (gerdy tubercle)

Innervation: superior gluteal nerve (L4, L5, S1)

Action: flexes hip joint; acts with gluteus maximus to stabilize the extended knee joint; pulls IT band

Fascia Lata

Layer of connective tissue overlying thigh muscles

Iliotibial tract

Band of longitudinal fibers on lateral side of fascia lata, connects distally to the lateral condyle of tibia

Piriformis

Origin: anterior surface of 2nd - 4th sacral segments; superior margin of greater sciatic notch and sacrotuberous ligament

Insertion: superior border of greater trochanter of femur

Innervation: branches of anterior rami of S1, S2

Action: laterally rotate extended hip joint; abduct flexed hip joint; steady femoral head in acetabulum (stabilizes hip joint)

Gemellus Superior

Origin: ischial spine

Insertion: medial surface of greater trochanter (trochanteric fossa) of femur

Innervation: nerve to obturator internus (L5, S1)

Action: laterally rotate extended hip joint; abduct flexed hip joint; steady femoral head in acetabulum (stabilizes hip joint)

Obturator Internus

Origin: pelvic surface of ilium and ischium; obturator membrane

Insertion: medial surface of greater trochanter (trochanteric fossa) of femur

Innervation: nerve of obturator internus (L5, S1)

Action: laterally rotate extended hip joint; abduct flexed hip joint; steady femur head into acetabulum (stabilizes hip joint)

Gemellus Inferior

Origin: ischial tuberosity

Insertion: medial surface of greater trochanter (trochanteric fossa) of femur

Innervation: nerve to quadratus femoris (L5, S1)

Action: laterally rotate extended hip joint; abduct flexed hip joint; steady femoral head in acetabulum (stabilizes hip joint)

Quadratus Femoris

Origin: lateral border of ischial tuberosity

Insertion: quadrate tubercle on intertrochanteric crest of femur

Innervation: nerve to quadratus femoris (L5, S1)

Action: laterally rotates hip joint; also pulls femoral head into acetabulum to stabilize hip joint

Sartorius

Origin: anterior superior iliac spine and superior part of notch inferior to it

Insertion: superior part of medial surface of tibia

Innervation: femoral nerve (L2, L3)

Action: flexes, abducts and laterally rotates hip joint; flexes knee joint

Quadriceps Femoris

Muscle group associated with movement of the knee (and hip)

Rectus Femoris

Origin: anterior inferior iliac spine and ilium superior to acetabulum

Insertion: via common tendinous (quadriceps tendon) and independent attachments to base of patella; indirectly via patellar ligament to tibial tuberosity

Innervation: femoral nerve (L2, L3, L4)

Action: extends knee joint; stabilizes hip joint and helps iliopsoas flex hip joint

Vastus Intermedius

Origin: anterior and lateral surfaces of shaft of femur

Insertion: via common tendinous (quadriceps tendon) and independent attachments to base of patella; indirectly via patellar ligament to tibial tuberosity

Innervation: femoral nerve (L2, L3, L4)

Action: extends knee joint

Vastus Lateralis

Origin: greater trochanter of femur and lateral lip of linea aspera

Insertion: via common tendinous (quadriceps tendon) and independent attachments to base of patella; indirectly via patellar ligament to tibial tuberosity; tibia and patella via aponeorses (lateral patella retinacula)

Innervation: femoral nerve (L2, L3, L4)

Action: extends knee joint

Vastus Medialis

Origin: intertrochanteric line and medial lip of linea aspera

Insertion: via common tendinous (quadriceps tendon) and independent attachments to base of patella; indirectly via patellar ligament to tibial tuberosity; tibia and patella via aponeorses (medial patella retinacula)

Innervation: femoral nerve (L2, L3, L4)

Action: extends knee joint

Quadriceps Tendon

common tendon for quadriceps group, attaches to patella

Patellar Ligament

transfers action of quadriceps muscles from patella to tibia

Pectineus

Origin: superior ramus of pubis

Insertion: pectineal line of femur, just inferior to lesser trochanter

Innervation: femoral nerve (L2, L3)

Action: adducts and flexes hip joint; assists with medial rotation of hip joint

Adductor Longus

Origin: body of pubis inferior to pubic crest

Insertion: middle third of linea aspera of femur

Innervation: obturator nerve (L2, L3, L4)

Action: adducts hip joint

Adductor Magnus

Origin: inferior ramus of pubis and ramus of ischium (adductor part), ischial tuberosity (hamstring part)

Insertion: gluteal tuberosity, linea aspera, and medial supracondylar line(adductor part), adductor tubercle of femur (hamstring part)

Innervation: obturator nerve(L2, L3, L4) (adductor part) tibial part of sciatic nerve (L4) (hamstring part)

Action: adducts hip joint; adductor part flexes hip joint, hamstring part extends hip joint

Gracilis

Origin: body and inferior ramus of pubis

Insertion: superior part of medial surface of tibia

Innervation: obturator nerve (L2, L3)

Action: adducts hip joint, flexes knee joint and helps rotate it medially

Biceps Femoris

Biceps Femoris (Long Head)

Origin: ischial tuberosity

Insertion: lateral side of head of fibula; tendon is split at this site by fibular collateral ligament of knee

Innervation: tibial division of sciatic nerve (L5, S1, S2)

Action: flexes knee joint and rotates it laterally when knee is flexed; extends hip joint

Biceps Femoris (Short Head)

Origin: linea aspera and lateral supracondylar line of femur

Insertion: lateral side of head of fibula; tendon is split at this site by fibular collateral ligament of knee

Innervation: common fibular division of sciatic nerve (L5, S1, S2)

Action: flexes knee joint and rotates it laterally when knee is flexed; extends hip joint

Semimembranosis

Origin: ischial tuberosity

Insertion: posterior part of medial condyle of tibia; reflected attachment forms oblique popliteal ligament (to lateral femoral condyle)

Innervation: tibial division of sciatic nerve (L5, S1, S2)

Action: extends hip joint; flex knee joint and rotate the leg medially when knee is flexed; when hip and knee are flexed, can extend trunk

Semitendinosus

Origin: ischial tuberosity

Insertion: medial surface of superior part of tibia

Innervation: tibial division of sciatic nerve (L5, S1, S2)

Action: extend hip joint; flex knee joint and rotate the leg medially when knee is flexed; when hip and knee are flexed, can extend trunk

Tibialis Anterior (TA)

Origin: lateral condyle and superior 2/3 of lateral tibal surface, interroseous membrane

Insertion: medial and inferior suface of medial cuneiform and base of 1st metatarsal

Innervation: deep fibular nerve (L4, L5)

Action: primary dorsiflexor of ankle; primary inverter of foot; supports medial longitudinal ankle

Extensor Digitorum Longus (EDL)

Origin: lateral condyle of tibia and superior 2/3 of anterior suface of fibula and interosseous membrane

Insertion: middle and distal phalanges of lateral four digits (2-5)

Innervation: deep fibular nerve (L5, S1)

Action: extends lateral four digits; secondary dorsiflexor of ankle

Extensor Hallucis Longus (EHL)

Origin: middle part of anterior surface of fibula and interosseous membrane

Insertion: dorsal aspect of base of distal phalanx of great toe (hallux)

Innervation: deep fibular nerve (L5, S1)

Action: extends great toe; secondary dorsiflexor of ankle

Fibularis Longus (FL)

Origin: head and superior 2/3 of lateral surface of fibula

Insertion: base of 1st metatarsal and medial cuneiform

Innervation: superficial fibular nerve (L5, S1, S2)

Action: evert foot, weakly plantarflexes ankle; supports transverse arch of foot

Fibularis Brevis (FB)

Origin: middle part of lateral surface of fibula

Insertion: dorsal surface of tuberosity of base of 5th metatarsal

Innervation: superficial fibular nerve (L5, S1, S2)

Action: evert foot; weakly plantar flex ankle

Gastrocnemius

Origin: lateral aspect of lateral condyle of femur (lateral head), popliteal surface of femur, superior to medial condyle (medial head)

Insertion: posterior surface of calcaneus via calcaneal tendon

Innervation: tibial nerve (S1, S2)

Action: plantarflexes ankle when knee is extended; raises heel during walking; and flexes knee joint

Soleus

Origin: posterior aspect of head of fibula, superior quarter of posterior surface of fibula, soleal line, and medial border of tibia

Insertion: posterior surface of calcaneus via calcaneal tendon

Innervation: tibial nerve (S1, S2)

Action: plantar flexes ankle; steadies leg on foot

Plantaris

Origin: inferior end of lateral supracondylar line of femur and oblique popliteal ligament

Insertion: posterior surface of calcaneus via calcaneal tendon

Innervation: tibial nerve (S1, S2)

Action: weakly assists gastocnemius in plantarflexing ankle; function is probably mainly proprioceptive

Calcaneal Tendon

common tendon for the superficial posterior leg muscles

Popliteus

Origin: lateral surface of lateral condyle of femur and lateral meniscus (intra-articular; within cavity of knee joint)

Insertion: posterior surface of tibia, superior to soleal line

Innervation: tibial nerve (L4, L4, S1)

Action: weakly flexes knee and unlocks it by laterally rotating femur on fixed tibia, may also medially rotate tibia of unplanted limb (“key to the knee”)

Tibialis Posterior (TP)

Origin: interosseous membrane, posterior surface of tibia inferior to soleal line, and posterior surface of fibula

Insertion: primarily to tuberosity of navicular; also to cuneiforms, cuboid, and bases of 2nd - 4th metatarsals

Innervation: tibial nerve (L4, L5)

Action: plantarflexes ankle; primary inverter of foot; supports medial longitudinal arch of foot

Flexor Digitorum Longus

Origin: medial part of posterior surface of tibia inferior to soleal line and by a broad tendon to fibula

Insertion: bases of distal phalanges of lateral four digits

Innervation: tibial nerve (S2, S3)

Action: flexes lateral four digits; plantar flexes ankle; supports longitudinal arches of foot

Flexor Hallucis Longus

Origin: inferior 2/3 of posterior surface of fibula and inferior part of interosseous membrane

Insertion: base of distal phalanx of great toe (hallux)

Innervation: tibial nerve (S2, S3)

Action: flexes great toe at all joints; weakly plantarflexes ankle; supports medial longitudinal arch of foot

Extensor Digitorum Brevis

Origin: dorsal surface of calcaneus

Insertion: 2nd to 4th toes (at dorsal aponeurosis and bases of the middle phalanges)

Innervation: deep fibular nerve (L5, S1)

Action: extends the metatarsophalangeal (MTP) and proximal interphangeal (PIP) joints of the 2nd to 4th toes

Extensor Hallucis Brevis

Origin: dorsal surface of calcaneus

Insertion: 1st toe (at dorsal aponeurosis and proximal phalanx)

Innervation: deep fibular nerve (L5, S1)

Action: extends metotarsophalangeal (MTP) joints of 1st toe

Abductor Hallucis

Origin: medial tubercle of tuberosity of calcaneus, flexor retinaculum, and plantar aponeurosis

Insertion: medial side of base of proximal phalanx of 1st digit

Innervation: medial plantar nerve (S2, S3)

Action: abducts and flexes hallux

Adductor Hallucis

Origin: oblique head from base of metatarsals 2-4; transverse head from plantar ligaments of 3rd-5th metatarsophalangeal joints

Insertion: tendons of both heads attach to lateral side of base of proximal phalanx of 1st digit

Innervation: deep branch of lateral plantar nerve (S2, S3)

Action: adducts 1st digit; assists in maintaining transverse arch of foot

Flexor Hallucis Brevis

Origin: plantar surfaces of cuboid and lateral cuneiform

Insertion: both sides of base of proximal phalanx of 1st digit

Innervation: medial plantar nerve (S2, S3)

Action: flexes proximal phalanx of 1st digit

Abductor Digiti Minimi

Origin: medial and lateral tubercles of tuberosity of calcaneus, plantar aponeurosis, and intermuscular septa

Insertion: lateral side of base of proximal phalanx of 5th digit

Action: abducts and flexes 5th digit

Flexor Digiti Minimi Brevis

Origin: base of 5th metatarsal

Insertion: base of proximal phalanx of 5th digit

Innervation: superficial branch of lateral plantar nerve (S2, S3)

Action: flexes proximal phalanx of 5th digit, thereby assisting with its flexion

Plantar Aponeurosis

broad CT sheet coverin plantar surface of foot

Flexor Digitorum Brevis

Origin: medial tubercle of tubersoty of calcaneus, plantar aponeurosis, and intermuscular septa

Insertion: both sides of middle phalanges of lateral four digits

Innervation: medial plantar nerve (S2, S3)

Action: flexes digits II-V (lateral four digits)

Quadratus Plantae

Origin: medial surface and lateral margin of plantar surface of calcaneus

Insertion: posterolateral margin of tendon of flexor digitorum longus

Innervation: lateral plantar nerve (S2, S3)

Action: assits flexor digitorum longus in flexing lateral four digits

Lumbricals (4)

Origin: tendons of flexor digitorum longus

Inserion: medial aspect of expansion over lateral four digits

Innervation: medial plantar nerve (S2, S3; medial one) lateral plantar nerve (S2, S3; lateral three)

Action: flex proximal phalanges; extend middle and distal phalanges of lateral four digits

Plantar Interossei (three muscles)

Origin: bases and medial sides of metatarsals 3-5

Insertion: medial side of bases of proximal phalanges of 3rd-5th digits

Innervation: lateral plantar nerve (S2, S3)

Action: adduct digits (3-5) and flex metatarsophalangeal joints

Dorsal Interossei (four muscles)

Origin: adjacent sides of metatarsals 1-5

Insertion: medial side of proximal phalanx of 2nd digit (first), lateral sides of 2nd-4th digits (second to fourth)

Innervation: lateral plantar nerve (S2, S3)

Action: abduct digits (2-4) and flex metatarsophalangeal joints

Superficial Layer of Back Muscles

Splenius Capitis and Splenius Cervicis

Splenius (capitis and cervicis)

Origin: arises from nuchal ligament and spinous processes of C7-T6 vertebrae

Insertion: mastoid process of temporal bone and superior nuchal line of occipital bone (capitis), tubercles of transverse processes of C1-C3 or C4 vertebrae (cervicis)

Innervation: posterior rami of spinal nerves

Action: laterally flex, rotate to same side (unilateral), extend head and neck (bilateral)

Intermediate Layer of Back Muscles

Erector Spinae: Iliocostalis, Longissimus, Spinalis (lateral to medial)

Erector Spinae

Iliocostalis, Longissimus, Spinalis

Origin: posterior part of iliac crest, posterior surface of sacrum, sacro-iliac ligaments, sacral and inferior lumbar spinous processes and supraspinous ligaments

Insertion: lower ribs and cervical transverse processes (iliocostalis; luborum, thoraces, and cervicis), ribs and transverse processes in thoracic and cervical regions and mastoid process of temporal bone (longissimus; thoracis, cervicis, and capitis), spinous processes in upper thoracic region to cranium (spinalis; thoracis, cervicis, and capitis)

Innervation: posterior rami of spinal nerves

Action: laterally flex, rotate to same side (unilateral), extend (bilateral)

Deep Layer of Back Muscles

Transversospinales: Semispinalis (thoracis, cervicis, and capitis), Multifidus, Rotores (brevis and longus)

Transversospinales

Semispinalis, Multifidus, Rotatores → stability and posture muscles of back

Semispinalis (thoracis, cervicis, and captitis)

Origin: transverse processes of C4-T10

Insertion: occipital bone, spinous processes in upper thoracic and cervical regions

Innervation: posterior rami of spinal nerves
Action: facilitates contralateral rotation (unilateral), extends head, neck, and thoracic regions (bilateral); stability and posture

Multifidus

Origin: posterior sacrum, superior iliac spine of ilium, aponeurosis of erector spinae, sacro-iliac ligaments, mammilary processes of lumbar vertebrae, transverse processes of thoracic vertebrae, and articular processes of C4-C7

Insertion: spinous processes of vertebrae located two to four segments superior to origin

Innervation: posterior rami of spinal nerves

Action: laterally flex, rotate to opposite side (unilateral), extend (bilateral); stability and posture

Rotares (brevis and longus)

Origin: transverse processes of (thoracic) vertebrae

Insertion: spinous process of vertebra immediately (brevis) or two segments (longus) superior to vertebra of origin

Innervation: posterior rami of spinal nerves

Action: laterally flex, rotate to opposite side (unilateral), extend (bilateral); stability and posture

Minor Deep Layer of Back Muscles

Levator costorum, Lumbar interspinalis, Lumbar intertransversarii

Levator Costorum (action and innervation)

Unilateral: elevate ribs (during inspiration), laterally flex

Bilateral: extension

Innervation: posterior rami of spinal nerves

Lumbar Interspinales (action and innervation)

Action: extension

Innervation: posterior rami of spinal nerves

Lumbar Intertransversarii (action and innervation)

Unilateral: lateral flexion

Bilateral: extension

Innervaiton: posterior and anterior rami of spinal nerves

Rectus Capitis Posterior Major (action and innervation)

Action: extends and rotates the head

Innervation: suboccipital nerve (dorsal ramus of C1)

Rectus Capitis Posterior Minor (action and innervation)

Action: extends the head

Innervation: suboccipital nerve (dorsal ramus of C1)

Obliquus Capitis Superior (action and innervation)

Action: extends and laterally flexes the head

Innervation: suboccipital nerve (dorsal ramus of C1)

Obliquus Capitis Inferior (action and innervation)

Action: rotates the atlas (C1)

Innervation: suboccipital nerve (dorsal ramus of C1)