Avulsion Fractures (ASIS, AIIS, Ischial Tuberosity)


An avulsion fracture is caused by the strong contraction of a large muscle that results in separation of the bone at the attachment site of the tendon. The pelvis consists of multiple anatomical sites that are attachment points to large tendons and therefore have an increased risk of avulsion injuries. These types of avulsion injuries are commonly seen in adolescent athletes.

The following is the most common avulsion sites of the pelvis and the muscle associated in causing these fractures:

Anterior Superior Iliac Spine (ASIS) – Sartorius Muscle
Anterior Inferior Iliac Spine (AIIS) – Rectus femoris muscle (Quadrecips)
Ischial Tuberosity – Biceps femoris muscle (Hamstring)

Signs and Symptoms:

  • Sharp deep pain felt over affected tendon site.
  • Usually a sudden onset with strong pain that stops an individual from continuing activity/sport.
  • Muscle weakness of the primary muscle being involved in the injury.
  • Difficulty in walking and standing when acute.

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