Gluteal Region and Sciatic Nerve: Anatomy and Clinical Injections

Overview

The gluteal region lies posterior to the pelvis, bounded superiorly by the iliac crest and inferiorly by the gluteal fold. It is the most common site for intramuscular (IM) injections, making understanding of its neurovascular anatomy essential for every clinician.

Surface Landmarks

• Iliac crest: Forms the upper border
• Posterior superior iliac spine (PSIS): Marks the S2 level; dimple of Venus
• Greater trochanter: Lateral prominence
• Gluteal fold: NOT the inferior border of gluteus maximus (the muscle extends ~7 cm below the fold)
• Ischial tuberosity: Palpable in flexion (sitting position); covered by gluteus maximus in standing

Safe Quadrant for IM Injection

Divide the buttock into four quadrants using a vertical line from the PSIS and a horizontal line through the greater trochanter. Inject ONLY into the upper outer (superolateral) quadrant to avoid:

• Sciatic nerve (midline, midway between greater trochanter and ischial tuberosity)
• Superior and inferior gluteal arteries and nerves

Clinical note: Modern guidelines favor the ventrogluteal site (between iliac crest, ASIS, and greater trochanter) over dorsogluteal due to thinner fat layer and absence of major neurovascular structures.

Muscles of the Gluteal Region

Superficial Group

1. Gluteus maximus

   • Largest muscle in the body
   • Innervation: Inferior gluteal nerve (L5, S1, S2)
   • Actions: Powerful hip extension, lateral rotation
   • Insertion: Gluteal tuberosity of femur + iliotibial tract
   • Tested by: Climbing stairs, rising from sitting

2. Gluteus medius and minimus

   • Innervation: Superior gluteal nerve (L4, L5, S1)
   • Actions: Hip abduction and medial rotation
   • Insertion: Greater trochanter
   • Trendelenburg test: When standing on one leg, the opposite hip drops if these muscles are weak (or the superior gluteal nerve is damaged) — indicates lesion of superior gluteal nerve or L5 radiculopathy

Deep Group (lateral rotators)