The anterior superior iliac spine (ASIS) is a bony prominence and key anatomical landmark on the human body. It is widely recognized in fields from physical therapy to surgery. This article clarifies the ASIS’s location and its importance in human anatomy and health.
Anatomical Position
The anterior superior iliac spine is a distinct bony projection at the front of the pelvis. It is located on the ilium, the largest of the three fused bones forming each hip bone. This structure is easily felt just beneath the skin, making it a prominent feature in surface anatomy.
This spine marks the most anterior point of the iliac crest, the curved upper border of the ilium. The iliac crest extends from the ASIS at the front to the posterior superior iliac spine (PSIS) at the back of the pelvis. The ASIS is situated near the hip joint.
How to Locate It
Locating the anterior superior iliac spine involves a simple palpation technique. Place your hands on your hips, at the top, wide part of your hip bones (the iliac crest). Gently slide your fingers forward along this bony ridge towards the front of your body.
As your fingers move forward and slightly downward, you will feel a distinct, curved bony knob or prominence. This is the anterior superior iliac spine, often described as the “first lump” felt when moving superiorly from the anterior midline of the thighs. This prominence is found at the lateral end of the inguinal fold, a crease that runs diagonally from the hip towards the groin. Gently pressing on this area will confirm the bony feel of the ASIS.
Why This Landmark Matters
The anterior superior iliac spine serves as an attachment point for several muscles and a ligament. The sartorius muscle, the longest muscle in the body, originates here, as does the tensor fasciae latae muscle. The inguinal ligament, a strong band of connective tissue spanning the groin, attaches between the ASIS and the pubic tubercle.
Beyond its role in muscle and ligament attachments, the ASIS is a reference point in clinical assessments. It is used to measure true leg length, with measurements taken from the ASIS to the medial malleolus (inner ankle bone). Clinicians utilize the ASIS for assessing pelvic alignment, analyzing posture, and as a guide for medical procedures, including injections and surgical approaches to the hip and pelvis. The area near the ASIS on the iliac crest is also a common site for harvesting bone grafts used in orthopedic surgeries.