2c - Muscles in the Medial and Posterior Thigh

Question 1

Pectineus - Origin, Insertion, Action(s), and Innervation

Answer 1

Origin: Pectineal line of the pubis
Insertion: Along lesser trochanter to linea aspera
Primary action: Adducts, flexes, and medially rotates thigh
Innervation: Femoral and sometimes Obturator

Question 2

Adductor longus - Origin, Insertion, Action(s), and Innervation

Answer 2

Origin: Pubis
Insertion: Linea aspera
Primary action: Adducts, flexes, and medially rotates thigh
Innervation: Obturator

Question 3

Gracilis - Origin, Insertion, Action(s), and Innervation

Answer 3

Origin: Inferior ramus, body of pubis, and ischial ramus
Insertion: Medial surface of tibia
Primary action: Adducts thigh, flexes and medially rotates leg (especially during walking)
Innervation: Obturator

Question 4

Adductor brevis - Origin, Insertion, Action(s), and Innervation

Answer 4

Origin: Inferior ramus and body of pubis
Insertion: Linea aspera
Primary action: Adducts and medially rotates thigh
Innervation: Obturator

Question 5

Adductor magnus - Origin, Insertion, Action(s), and Innervation

Answer 5

Origin: Ischial tuberosity, ischial and pubic rami.
Insertion: Linea aspera; supracondylar line adductor tubercle.
Primary action: Anterior fibers [Adduct, flex, and medially rotate thigh], Posterior fibers [Synergist of hamstrings during thigh extension]
Innervation: Obturator and Sciatic

Question 6

Gluteus maximus - Origin, Insertion, Action(s), and Innervation

Answer 6

Origin: Dorsal ilium, sacrum, and coccyx
Insertion: Gluteal tuberosity, iliotibial tract
Primary action: Major extensor of thigh. Abducts and laterally rotates thigh.
Innervation: Inferior gluteal

Question 7

Gluteus medius - Origin, Insertion, Action(s), and Innervation

Answer 7

Origin: Between anterior and posterior gluteal lines on lateral surfaces of ilium
Insertion: Via tendon into into greater trochanter
Primary action: Abducts and medially rotates thigh. Steadies pelvis during walking
Innervation: Superior gluteal

Question 8

Gluteus minimus - Origin, Insertion, Action(s), and Innervation

Answer 8

Origin: Between anterior and inferior gluteal lines on external surface of ilium
Insertion: Greater trochanter
Primary action: Abducts and medially rotates thigh. Steadies pelvis during walking
Innervation: Superior gluteal

Question 9

Biceps femoris - Origin, Insertion, Action(s), and Innervation

Answer 9

Origin: Long head [ischial tuberosity and linea aspera] short head [distal femur]
Insertion: Via common tendon into head of fibula and lateral condyle of tibia
Primary action: Extend thigh, flexes knee, and laterally rotates leg
Innervation: Sciatic nerve divisions: tibial to long head, fibular to short head

Question 10

Semitendinosus - Origin, Insertion, Action(s), and Innervation

Answer 10

Origin: Ischial tuberosity
Insertion: Medial aspect of upper tibial shaft
Primary action: Extends thigh, flexes knee, and medially rotates leg
Innervation: Sciatic (tibial branch)

Question 11

Semimembranosus - Origin, Insertion, Action(s), and Innervation

Answer 11

Origin: Ischial tuberosity
Insertion: Medial condyle of tibia to lateral condyle of femur
Primary action: Extends thigh, flexes knee, and medially rotates leg
Innervation: Sciatic (tibial branch)

Question 12

What is the iliotibial tract?

Answer 12

A thickened portion of the fascia lata (fascia that ensheathes all thigh muscles). It’s a tendinous band spanning from iliac crest to the knee.