The Posterior Compartment of the Thigh

3 muscles of posterior thigh

• Biceps femoris (long head and short head)

• Semimembranosus

• Semitendinosus

Actions - posterior compartment muscles

Knee flexion, hip extension

Posterior thigh nerves

• Sciatic nerve

Posterior thigh - arterial supply

• No major artery

• Blood supply from 3-4 perforating branches of profunda femoris artery

Bicep femoris - long head

Origin: inferior medial aspect of upper ischial tuberosity

Insertion: head of fibula

Nerve supply: sciatic nerve - tibial divison

Nerve roots: L5, S1, S2

Biceps femoris - short head

Origin: shaft of femur - lateral lip of linea aspera

Insertion: head of fibula

Nerve supply: sciatic nerve - common peroneal division

Nerve roots: L5, S1, S2

Semitendinosus

Origin: inferior medial aspect of upper ischial tuberosity

Insertion: anteromedial surface of proxmial tibia

Nerve supply: sciatic nerve - tibial division

Nerve roots: L5, S1, S2

Semimembranosus

Origin: superolateral impression on ischial tuberosity

Insertion: posterior surface of medial tibial condyle

Nerve supply: sciatic nerve - tibial divison

Nerve roots: L5, S1, S2

The sciatic nerve

• Only major nerve in posterior compartment

• Travels below long head of biceps femoris on the posterior surface of adductor magnus

Sciatic nerve - separation

• Separates out into the tibial and common peroneal nerves at the upper border of the popliteal fossa

• But may separate higher up in thigh

Nerve supply - posterior thigh muscles

Sciatic nerve - tibial divison

• Long head (L5-S2)

• Semitendinosus (L5-S2)

• Semimembranosus (L5-S2)

Sciatic nerve - common peroneal division

• Short head biceps femoris (L5-S2)