The iliac crest is a prominent, easily felt bony structure that forms the upper boundary of the hip bones. This curved ridge serves as a fundamental landmark for understanding the body’s physical architecture and orienting oneself to the pelvic girdle. This guide provides clear instructions on how to locate the iliac crest and explains its practical relevance.
What Is the Iliac Crest?
The iliac crest is the thick, arched superior border of the ilium, the largest of the three bones that form the hip bone, or pelvic girdle. It is the top edge of the hip bone felt when placing hands on the waist. This ridge extends laterally from the front of the body, curving backward toward the spine.
This entire border is easily palpable because it lies close to the skin surface, with minimal soft tissue covering it. The crest begins anteriorly at a small projection known as the Anterior Superior Iliac Spine (ASIS) and terminates posteriorly at the Posterior Superior Iliac Spine (PSIS). Its curved shape and exposed position make it a reliable reference point for anatomical study and physical movement.
The iliac crest also serves as an attachment site for many powerful muscles. Abdominal muscles, such as the external and internal obliques, attach along this ridge, as do back muscles like the latissimus dorsi. This network of attachments highlights its role in providing stability and assisting in trunk movement.
Step-by-Step Guide to Finding the Crest
Begin by standing comfortably or lying on your back, as either position allows for clear access to the sides of the waist. Place your hands on your sides, where you would instinctively put them when saying, “Put your hands on your hips.” Your fingers should point toward the front of your body, and your thumbs should point toward the back.
Slowly slide your hands downward from the lower ribs until you feel the first firm, curved resistance of bone. This hard upper edge, felt through the soft tissue of the flank, is the superior border of the iliac crest. Apply gentle but firm pressure to confirm the structure is bone.
To locate the anterior starting point, continue to follow the crest forward with your fingertips. You will encounter a distinct, sharp bony protrusion at the very front of the hip, which is the Anterior Superior Iliac Spine (ASIS). This point marks the end of the crest’s forward curve.
The entire length of the crest can be traced by sweeping your hand backward from the ASIS along the side of your body. Following the crest to the back of the pelvis leads to the Posterior Superior Iliac Spine (PSIS), which is less prominent but can sometimes be felt as a small dimple just above the buttocks. Tracing the full curve confirms you have located the entire bony landmark.
Practical Uses of This Bony Landmark
Locating the iliac crest is helpful for general body awareness and is often used as a standard reference point for measurements. For instance, the widest part of the hips, needed for clothing sizes or fitness assessments, is measured across the prominence of the iliac crests. The top of the crest also approximates the natural waistline, guiding where pants or skirts should sit.
In the context of fitness and posture, the iliac crest is invaluable for monitoring pelvic alignment. Observing the height and tilt of the crests helps individuals understand if they are standing with a neutral, anterior, or posterior pelvic tilt. Maintaining a level crest is a common cue for core engagement and proper posture during exercises.
Health professionals also rely on this structure as a fixed reference point for various assessments. A line drawn horizontally between the highest points of the two iliac crests, known as the supracristal plane, reliably approximates the level of the fourth lumbar vertebra (L4). This anatomical consistency makes the crest a simple tool for external body mapping, useful for assessing leg length discrepancies or spinal alignment.