Lower limb muscles

Question 1

Psoas major

Answer 1

• Origin - transverse processes of L1-L5
• Insertion - lesser trochanter of femur
• Action - flexes thigh at hip
• Innervation - Anterior rami of L1-L3

Question 2

Iliacus

Answer 2

• Origin - iliac fossa
• Insertion - lesser trochanter of femur
• Action - flexes thigh at hip
• Femoral nerve (L2, L3, L4)

Question 3

Tensor fasciae latae

Answer 3

• Origin - ASIS and anterior portion of iliac crest
• Insertion - iliotibial tract (inserts onto lateral condyle of tibia)
• Action - flexes, abducts and medially rotates the thigh. Stabilises hip joint and extended knee
• Innervation - superior gluteal nerve (L4 and L5)

Question 4

Sartorius

Answer 4

• Origin - ASIS
• Insertion - Superior portion of medial surface of tibial shaft
• Action - flexes, abducts and laterally rotates thigh. Flexes leg at knee joint. Think of sitting cross-legged on floor.
• Innervation - femoral nerve (anterior rami of L2 and L3)

Question 5

Rectus femoris

Answer 5

• Origin - AIIS and ilium superior to acetabulum (2 heads)
• Insertion - quadriceps tendon (inserts into base of patella and into tibial tuberosity via patellar ligament)
• Action - extends leg at knee joint
• Innervation - femoral nerve (L2, L3, L4)

Question 6

Vastus lateralis

Answer 6

• Origin - greater trochanter of femur and lateral lip of linea aspera
• Insertion - lateral patella and tendon of rectus femoris
• Action - Extends leg at knee
• Innervation - femoral nerve (L2, L3, L4)

Question 7

Vastus intermedius

Answer 7

• Origin - anterior and lateral aspects of femoral shaft
• Insertion - posterior surface of upper border of patella and forms part of quadriceps tendon
• Action - extends leg at knee
• Innervation - femoral nerve (L2, L3, L4)

Question 8

Vastus medialis

Answer 8

• Insertion - intertrochanteric line and medial lip of linea aspera of femur
• Origin - medial border of quadriceps tendon and medial side of patella
• Action - extends leg at knee joint
• Innervation - femoral nerve (L2, L3, L4)

Question 9

Pectineus

Answer 9

• Origin - pectineal line of pubic bone
• Insertion - pectineal line on posterior aspect of femur inferior to lesser trochanter
• Action - adducts and flexes thigh at hip joint
• Innervation - femoral nerve (L2 and L3)

Question 10

Adductor longus

Answer 10

• Origin - body of pubic bone, just beneath pubic tubercle
• Insertion - linea aspera of femur
• Action - adducts thigh, flexes and medially rotates thigh
• Innervation - obturator nerve (L2, L3, L4)

Question 11

Adductor brevis

Answer 11

• Origin - body and inferior ramus of pubis
• Insertion - pectineal line and proximal portion of linea aspera of femur
• Action - adducts thigh at hip joint, flexes and medially rotates thigh
• Innervation - obturator nerve (L2, L3, L4)

Question 12

Obturator externus

Answer 12

• Origin - obturator foramen and obturator membrane
• Insertion - intertrochanteric fossa
• Action - laterally rotates thigh and steadies head of femur in acetabulum
• Innervation - obturator nerve (L3 and L4)

Question 13

Adductor magnus

Answer 13

• Origin - inferior ramus of pubis, ramus of ischium, ischial tuberosity
• Insertion - linea aspera, medial supracondylar line (adductor portion), adductor tubercle of femur (hamstring portion
• Action - adducts thigh at hip
• Innervation - obturator nerve (L2, L3, L4 - adductor portion) and tibial portion of sciatic nerve (L4 - hamstring portion)

Question 14

Gracilis

Answer 14

• Origin - body and inferior ramus of pubis
• Insertion - medial aspect of upper portion of tibia
• Action - adducts thigh, flexes leg at knee, medially rotates leg when knee is flexed
• Innervation - Obturator nerve

Question 15

What is the pes anserinus?

Answer 15

• Expanded insertion of sartorius, semitendinosus and gracilis

Question 16

Gluteus maximus

Answer 16

• Origin - gluteal surface of sacrum, ilium and coccyx
• Insertion - iliotibial tract, gluteal tuberosity of femur
• Action - powerful extensor and lateral rotator of thigh
• Innervation - inferior gluteal nerve (L5, S1 and S2)

Question 17

Gluteus medius

Answer 17

• Origin - gluteal surface of ilium
• Insertion - greater trochanter of femur
• Action - strong abductor and medial rotator of thigh at hip joint
• Innervation - superior gluteal nerve (L5 and S1)

Question 18

Gluteus minimus

Answer 18

• Origin - gluteal surface of ilium
• Insertion - greater trochanter of femur
• Action - abducts and medially rotates thigh
• Innervation - superior gluteal nerve (L5 and S1)

Question 19

Piriformis

Answer 19

• Origin - 2nd, 3rd, 4th sacral segments and sacrotuberous ligaments
• Insertion - greater trochanter of femur
• Action - abducts flexed thigh at hip and laterally rotates extended thigh
• Nerve to piriformis (anterior rami of S1 and S2)

Question 20

Gemelli

Answer 20

• Origin - spine of ischium (superior gemellus) and ischial tuberosity (inferior gemellus)
• Insertion - greater trochanter of femur
• Action - laterally rotate extended thigh and abduct flexed thigh
• Innervation - nerve to obturator internus (L5 and S1, superior gemellus) and nerve to quadratus femoris (L5 and S1, inferior gemellus)

Question 21

Obturator internus

Answer 21

• Origin - pubis and ischium at obturator foramen
• Insertion - greater trochanter of femur
• Action - laterally rotates extended thigh at hip joint and abducts flexed thigh at hip
• Innervation - nerve to obturator internus (L5 and S1)

Question 22

Quadratus femoris

Answer 22

• Origin - lateral border of ischial tuberosity
• Insertion - quadrate tubercle on intertrochanteric crest of femur
• Action - rotates thigh laterally
• Innervation - nerve to quadratus femoris (L5 and S1)

Question 23

Semitendinosus

Answer 23

• Origin - ischial tuberosity
• Insertion - medial surface of tibia
• Action - flexes leg at knee, medially rotates flexed leg and extends thigh at hip joint
• Innervation - Sciatic nerve, tibial division (L5, S1, S2)

Question 24

Semimembranosus

Answer 24

• Origin - ischial tuberosity
• Insertion - medial condyle of tibia
• Action - flexes leg at knee, medially rotates flexed leg, and extends thigh at hip joint
• Innervation - Sciatic nerve, tibial division (L5, S1, S2)

Question 25

Biceps femoris

Answer 25

• Origin - ischial tuberosity (long head) and linea aspera and lateral supracondylar line (short head)
• Insertion - lateral side of head of fibula
• Action - flexes leg at knee, laterally rotates flexed leg, extends thigh at hip
• Innervation - Sciatic nerve, tibial division (L5, S1, S2 - long head) and common fibular division (L5, S1, S2 - short head)

Question 26

Fibularis longus

Answer 26

• Origin - superior and lateral surface of fibula and lateral tibial condyle
• Insertion - base of 1st metatarsal and medial cuneiform bone
• Action - everts foot and is a weak plantarflexor
• Innervation - Superficial fibular nerve (L5, S1, S2)

Question 27

Fibularis brevis

Answer 27

• Origin - distal 2/3 of lateral surface of fibular shaft
• Insertion - tuberosity on lateral side of base of 5th metatarsal
• Action - everts foot and acts as a weak plantarflexor
• Innervation - Superficial fibular nerve (L5, S1, S2)

Question 28

Tibialis anterior

Answer 28

• Origin - lateral condyle and lateral surface of tibia and interosseus membrane
• Insertion - medial cuneiform and base of metatarsal I
• Action - dorsiflexes foot and inverts foot
• Innervation - deep fibular nerve (L4 and L5)

Question 29

Extensor hallucis longus

Answer 29

• Origin - medial surface of fibular shaft and interosseus membrane
• Insertion - base of distal phalanx of big toe
• Action - extends big toe and dorsiflexes foot
• Innervation - deep fibular nerve (L5 and S1)

Question 30

Extensor digitorum longus

Answer 30

• Origin - lateral condyle of tibia, medial surface of fibula and interosseus membrane
• Insertion - divides into 4 tendons that insert onto middle and distal phalanges of toes 2-5
• Action - extends proximal phalanges of lateral 4 toes and dorsiflexes foot
• Innervation - deep fibular nerve (L5 and S1)

Question 31

Gastrocnemius

Answer 31

• Origin - lateral head arises from lateral femoral condyle and medial head arises from medial femoral condyle
• Insertion - 2 heads combine to form a single muscle belly and converge with soleus to form calcaneal tendon. This inserts onto calcaneus.
• Action - plantarflexes foot, flexes leg at knee and raises heel during walking
• Innervation - tibial nerve (S1 and S2)

Question 32

Soleus

Answer 32

• Origin - soleal line of tibia and proximal fibula
• Insertion - combines with gastrocnemius to form calcaneal tendon. This then inserts onto calcaneus.
• Action - plantarflexes foot at ankle, important postural muscle
• Innervation - tibial nerve (S1 and S2)

Question 33

Plantaris

Answer 33

• Origin - lateral supracondylar line of femur
• Insertion - blends with calcaneal tendon and inserts onto calcaneus
• Action - assists in plantarflexion of foot and flexion of leg
• Innervation - tibial nerve (S1 and S2)

Question 34

Popliteus muscle

Answer 34

• Origin - lateral condyle of femur and lateral meniscus of knee joint
• Insertion - posterior surface of tibia, superior to soleal line
• Action - lateral rotation of the femur relative to the tibia. This ‘unlocks’ the knee joint so that flexion can occur.
• Innervation - tibial nerve (L4, L5 and S1)

Question 35

Flexor hallucis longus

Answer 35

• Origin - Posterior surface of fibula
• Insertion - base of distal phalanx of big toe
• Action - flexes distal phalanx of big toe, plantarflexes foot at ankle, helps propel foot during walking or running
• Innervation - Tibial nerve (S2 and S3)

Question 36

Flexor digitorum longus

Answer 36

• Origin - medial surface of tibia
• Insertion - base of distal phalanx of each of the lateral 4 digits
• Action - flexes lateral 4 toes and assists in plantarflexion of ankle and inversion of midfoot
• Innervation - tibial nerve (S2 and S3)

Question 37

Tibialis posterior

Answer 37

• Origin - posterior surface of interosseus membrane
• Insertion - plantar surface of navicular and medial cuneiform bones
• Action - inverts and plantarflexes foot and maintains medial arch of foot
• Innervation - tibial nerve (L4 and L5)