3. Muscles of the back of thigh

4. Sciatic nerve Root value: sacral plexus (L4,5, S1,2,3).
Course & relations:
It passes through the greater sciatic foramen (below piriformis).
Passes deep to glut maximus.
Passes deep to hamstrings.

5. Branches Muscular: 1-Tibial N. 2-Common peroneal N.
From med side: biceps (long head), semitendinousus, semimembranosus, adductor magnus (ischial part).
From lat side: biceps (short head).
End: at lower 1/3 of thigh (sup angle of popliteal fossa) by dividing into:
1-Tibial N.
2-Common peroneal N.

6. Injury of sciatic Nerve
Motor:
paralysis of hamstrings → impaired knee flexion.
paralysis of all muscles below knee (tibial & common peroneal Ns) → foot drop.
Sensory: loss of sensation below knee (tibial& common peroneal Ns) except med side of leg & foot (saphenous N of femoral).

7. Popliteal fossa
Definition: diamond shaped space at the back of the knee.
Boundaries:
Superolateral: biceps.
Superomedial: semitendinosus & semimembranosus.
Inferolateral: gastrocnemius (lat head).
Inferomedial: gastrocnemius (med head).

10. Roof: skin, superficial fascia & deep fascia.
Floor:
1-Sup 1/3: femur (popliteal surface).
2-Middle 1/3: knee capsule.
3-Inf 1/3: popliteus muscle.

11. contents 1-Popliteal A: the deepest structure.
2-Popliteal V: superficial to the artery.
3-Tibial (med popliteal) N: passes superficial to popliteal vessels from sup to inf angles.
4-common peroneal (lat popliteal) N: passes from sup to lat angles near biceps.
5-Popliteal lymph nodes.

12. Common peroneal (lateral popliteal) nerve
Root value: Sacral plexus, L4,5,S1,2 (ant rami, post divisions).
Beginning: one of 2 terminal branches of sciatic N at lower 1/3 of back of thigh (sup angle of popliteal fossa).

13. Course &Relations -It enters popliteal fossa through the sup angle.
-Descends near the biceps.
-Leaves the fossa through the lat angle.
-Curves on the lat side of neck of fibula where it ends.

14. Branches
. Cutaneous:
1-Lat cutaneous N of calf: skin of lat & ant surfaces of the upper part of leg.
2-Sural communicating N: joins the sural N (of tibial).
Articular: knee.
Terminal branches: superficial & deep peroneal Ns.
End: It ends by dividing on the lat side of neck of fibula into superficial peroneal (musculocutaneous) & deep peroneal (ant tibial) Ns.

15. Injury
Cause: usually fracture neck of fibula. Motor: Paralysis of extensors of leg → foot drop. Paralysis of peroneal muscles → loss of eversion. Sensory: loss of sensation of: Ant & lat sides of leg. Dorsum of foot except med & lat borders. Dorsum of toes except lat side of little toe.