Posterior Thigh

Question 1

Give the origin, insertion, innervation, action, and test for:

Semitendinosus

Answer 1

Origin:
Ischial tuberosity

Insertion:
Pes Anserinus (Superior, medial tibia)

Innervation:
Tibial Part of Sciatic Nerve (L4,5,S1,2,3)

Action:

• Extend thigh
• Flex leg
• Medially rotate leg if it flexed
• If thigh + leg are flexed, can extend the trunk

Test:
Patient flexes leg against examiner resistance. Hamstring tendons on either side of the popliteal fossa should be visible (Medial side = Semitendinosus + Semimembranosus)

Question 2

Give the origin, insertion, innervation, action, and test for:

Semimembranosus

Answer 2

Origin:
Ischial tuberosity

Insertion:
Posterior part of medial condyle of tibia (reflected attachment forms transverse popliteal ligament)

Innervation:
Tibial part of Sciatic Nerve (L4,5,S1,2,3)

Action:

• Extend thigh
• Flex leg
• Medially rotate leg if it is flexed
• If leg and thigh is flexed, can extend trunk

Test:
Ask patient to flex leg against examiner resistance. Hamstring tendons can be seen on either side of the popliteal fossa (medial side = Semimembranosus + Semitendinosus)

Question 3

Give the origin, insertion, innervation, action, and test for:

Biceps Femoris

Answer 3

Origin:
Long head- Ischial Tuberosity
Short head- Inferior 1/3 of lateral lip of linea aspera + lateral Supracondylar line of femur

Insertion:
Lateral side of head of fibula (shared tendon is split due to fibular (lateral) collateral ligament).

Innervation:
Long head- Tibial part of Sciatic Nerve (L4,5,S1,2,3)
Short head- Common Peroneal (Fibular) Nerve (L4,5,S1,2)

Action:

• Extends thigh
• Flex leg
• Rotate leg laterally when it is flexed

Test:
Ask patient to flex leg against examiner resistance. Hamstring tendons visible either side of popliteal fossa (lateral side = biceps)

Question 4

Name the muscles in the posterior of the thigh

Answer 4

Semitendinosus
Semimembranous
Biceps Femoris (Long and Short heads)