Muscles of the Posterior Thigh

Question 1

Muscles

Answer 1

Biceps femoris
Semitendinosus
Semimembranosus

Question 2

Innervation

Answer 2

Sciatic nerve (L4-S3)

Question 3

Biceps femoris

Answer 3

• Origin - long head - ischial tuberosity of the pelvis / short head - linea aspera on posterior surface of the femur
• Insertion - head of the fibula
• Actions - flexion at the knee, extension of the leg at the hip, lateral rotation at hip and knee
• Innervation - long head - tibial part of sciatic nerve / short head - common fibular part of sciatic nerve

Question 4

Semitendinosus

Answer 4

• Origin - ischial tuberosity of pelvis
• Attachment - medial surface of tibia
• Actions - flexion of the leg at the knee, extension of thigh at hip, medial rotation of the thigh at the hip and the leg at the knee
• Innervation - tibial part sciatic nerve

Question 5

Semimembranosus

Answer 5

• Origin - ischial tuberosity more superiorly than semitendinosus and biceps femoris
• Attachment - medial tibial condyle
• Actions - flexion of leg at knee, extension of thigh at hip, medially rotates thigh at hip and leg at knee
• Innervation - tibial part of sciatic nerve

Question 6

Muscle strain

Answer 6

Excessive stretch or tearing of the hamstring muscle fibres
Often seen in athletes involved in running or kicking
Likely to rupture surrounding blood vessels -> haematoma contained by overlying fascia lata
RICE protocol

Question 7

Avulsion fracture of ischial tuberosity

Answer 7

Fragment of bone breaks away from main body of bone
Hamstring tendons tear off a piece of ischial tuberosity
Sports which require rapid contraction and relaxation of muscles (sprinting, football and hurdling)