3-26 Posterior Thigh Muscles

Question 1

what are the 4 muscles of the posterior thigh (3 are the hamstrings)

Answer 1

• semitendinosus
• semimembranosus
• biceps femoris (long head)
• biceps femoris (short head)

the short head is not considered part of the hamstrings

Question 2

what are the general origins + insertions of the hamstrings

Answer 2

origin = ischial tuberosity
insertions = bones of the leg

Question 3

what joints do the hamstrings cross

Answer 3

both the hip + knee joint
(general actions on next card)

Question 4

what are the general actions of the hamstring muscles

Answer 4

extend the hip + flex the knee
(as these muscles cross botht the hip + knee joint)

the short head of the femoris is not a hamstring muscle - primarily flexes the knee

Question 5

semitendinosus

Answer 5

proximal attachment:
ischial tuberosity

distal attachment:
medial surface of the superior part of tibia

innervation:
tibial division of sciatic nerve (L2-S2)

main actions:
- extends thigh at hip
- flexes leg at knee
- rotates leg medially
- can extend trunk when hip + knee flexed

Question 6

semimembranosus

Answer 6

proximal attachment:
ischial tuberosity

distal attachment:
posterior part of medial condoyle of tibia

innervation:
tibial division of sciatic nerve (L5-S2)

main actions:
- extends thigh at hip
- flexes leg at knee
- rotates leg medially
- can extend trunk when hip + knee flexed

Question 7

biceps femoris (long head)

Answer 7

proximal attachment:
ischial tuberosity

distal attachment:
lateral side of head of fibula

innervation:
tibial division of sciatic nerve (L5-S2)

main actions:
- flexes leg at knee
- rotates leg laterally
- extends thigh at hip (ie when one is starting to walk)

Question 8

biceps femoris (short head)

not considered one of the hamstrings

Answer 8

proximal attachment:
linea aspera of lateral supracondylar line of femur

distal attachment:
lateral side of head of fibula

innervation:
common fibular (peroneal) division of sciatic nerve (L5-S2)

main actions:
flexes the knee

Question 9

CC: intragluteal injections

Answer 9

• these are intramuscular injections
• common site as large muscle mass allows for venous absorbtion of the drug
• need to give superolaterally (upper-outer quadrant)
• this is to avoid injury to the large sciatic nerve or haematoma