Sciatic nerve

From Ganfyd

Roots

• From L4,L5,S1,S2,S3

Motor Supply

• semitendinosus
• biceps femoris
• semimembranosus
• adductor magnus

Then splits into tibial and common peroneal nerves

Sensory Supply

Path

1. emerges from pelvis below piriformis
2. curves laterally and downward through gluteal region
3. starts midway between
   • posterior superior iliac spine
   • ischial tuberosity
4. later midway between
   • tip of greater trochanter
   • ischial tuberosity
5. passes downward in midline on posterior aspect of thigh
6. passes deep to biceps femoris
7. divides into tibial nerve and common peroneal nerves about half way down thigh (variable)

Common Pathology

• misplaced injection in the buttocks
• hip replacement surgery
• sciatica

Findings

Motor

• hamstrings paralysed
• weak flexion of knee possible
  • sartorius and gracilis spared
• all muscles below knee paralysed
  • footdrop

Sensory

• loss of sensation below knee
  • except medial side lower leg (saphenous nerve)