The iliac crest forms the large, curved upper border of the ilium, the widest and uppermost of the three bones making up the pelvis. This bony ridge serves as an attachment point for numerous muscles, ligaments, and fascia. It plays an important role in supporting the trunk and connecting it to the lower limbs.
Anatomy of the Iliac Crest
The iliac crest is easily felt along the upper edge of the hip. It extends from the anterior superior iliac spine (ASIS) at its front to the posterior superior iliac spine (PSIS) at its back. The ASIS is a prominent, palpable bony projection marking the anterior end of the iliac crest. This broad surface provides attachment for various muscles and ligaments.
Muscles Attaching to the Iliac Crest
Several muscles attach to different parts of the iliac crest. The anterior superior iliac spine (ASIS) serves as an origin for the sartorius and tensor fasciae latae muscles. The sartorius flexes, abducts, and laterally rotates the hip, and flexes the knee. The tensor fasciae latae assists in hip flexion, abduction, and medial rotation, also stabilizing the hip and knee joints.
Along the lateral aspect of the iliac crest, the gluteus medius and gluteus minimus muscles originate from the outer surface of the ilium. The gluteus medius abducts and medially rotates the thigh. The gluteus minimus works with the gluteus medius to abduct and internally rotate the thigh. Both muscles stabilize the pelvis during walking.
Muscles of the abdominal wall, including the external abdominal oblique, internal abdominal oblique, and transversus abdominis, originate from the iliac crest. These muscles contribute to trunk movement and core stability. The latissimus dorsi originates partly from the posterior iliac crest, involved in arm adduction, extension, and internal rotation. The quadratus lumborum originates from the iliolumbar ligament and the inner lip of the iliac crest, contributing to lateral flexion and extension of the lumbar spine.
Contribution to Movement and Stability
The muscles attaching to the iliac crest collectively contribute to diverse movements of the trunk and lower limbs. The sartorius and tensor fasciae latae enable hip flexion. The gluteal muscles facilitate hip abduction and rotation. Abdominal muscles originating from the iliac crest are essential for trunk rotation and flexion.
These muscles also play a significant role in maintaining core stability, posture, and balance. The gluteus medius and minimus, for instance, stabilize the pelvis during single-limb support. The quadratus lumborum helps stabilize the spine and pelvis. This integrated muscular action is important for daily activities and athletic performances.
Understanding Iliac Crest Pain
Discomfort around the iliac crest can arise from various factors, often due to its role as an attachment point for numerous muscles and ligaments. Common causes include muscle strains or overuse injuries from repetitive movements. Inflammation of attached tendons and ligaments can also lead to pain. Trauma can directly damage the iliac crest or its surrounding structures.
Weakness in core muscles can contribute to iliac crest pain by offering poor support. This pain can manifest as lower back, hip, or pelvic pain, and may worsen with movement. Iliac crest pain can impact mobility and contribute to discomfort in the lower back or hip region.