The Anatomy of the Iliacus Muscle

The iliacus muscle is the triangle-shaped muscle in your pelvic bone that flexes and rotates your thigh bone. The iliacus is one of the most important hip flexor muscles in your body. It works with the other muscles in the hip and thigh to help you bend, run, walk, sit, and maintain correct posture.

This article describes where the iliacus muscle is located, what it does, and common medical conditions that can adversely affect its function, causing pain and stiffness.

Iliacus Muscle Anatomy

The iliacus muscle is part of a complex muscle system in the hip and pelvis. There are two iliacus muscles on each side of the pelvic bone that enable the flexion and rotation of the thigh. They are serviced by the femoral nerve, which provides movement and sensation to the lower limbs.

The iliacus muscle is situated on the largest of the three bones of the pelvis: the wing-shaped ilium. The muscle fits neatly into the curved surface of the ilium, called the iliac fossa.

The top of the iliacus muscle is attached to the upper "wings" of the ilium, called the iliac crest. It then extends down past the hip joint where it attaches to the upper thigh bone (femur) at a bony protrusion called the lesser trochanter.

The iliacus muscle is part of a major trio of muscles called the iliopsoas, which also includes the psoas major muscle and the psoas minor muscle. These sister muscles are also attached to the upper femur but extend upward past the ilium where they connect to the lumbar (lower) spine at several attachment points.

The iliopsoas also interact with the quadratus lumborum (QL) muscle, the deepest muscle of the lower back. The QL muscle starts at the iliac crest and, like the psoas major and minor muscles, attaches to the lumbar spine at several points.

The QL muscle enables flexion and elevation of the spine, while the iliopsoas enables the flexion and rotation of the hip and thigh.

Functions of the Iliacus Muscle

The iliacus muscle has many functions:

• It flexes and rotates the femur.
• It helps maintain proper body posture while standing or sitting.
• It provides hip flexion (bringing the knee to the chest).
• It enables the forward tilt of the pelvis and side-bending.
• It produces hip movement that enables walking, running, and climbing stairs.

Associated Conditions

There are several conditions that can adversely affect the iliacus muscle, particularly when it is underused or overused.

These conditions, referred to collectively as Iliopsoas syndrome, are typically the result of overuse or injury. These include iliopsoas tendinopathy, which affects tendons and iliopsoas bursitis, which affects cushioning sacs known as bursae.

Iliopsoas syndrome can affect anyone but is especially common in gymnasts, dancers, track-and-field athletes, and others who repeatedly use movements that flex the hips.

Iliopsoas Bursitis

Iliopsoas bursitis is the inflammation of the cushioning sac called a bursa situated under the iliacus muscle that helps it slide over the pelvic bone.

Symptoms can range from mild discomfort to pain that radiates through parts of the leg and hips. Runners, skiers, swimmers, and people with tight hips are commonly affected. People with different forms of arthritis can also be affected.

Early treatment can prevent the worsening of symptoms. Mild cases can be treated at home with rest, ice application, and over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs). Stretching can help relieve tightness.

In severe cases, treatment options may include:

• Physical therapy
• Prescription anti-inflammatory drugs
• Corticosteroid (steroid) injections
• Walking aids (such as a cane) to relieve pressure

Iliopsoas Tendinopathy

Iliopsoas tendinopathy is another condition that affects the iliacus muscles. This condition, experienced by dancers who repeatedly flex and hyperextend their hips, can result in hip and groin pain that gets worse with kicking or rotation.

It is sometimes referred to as "snapping hip syndrome" because you can hear an audible snapping sound.

The treatment of iliopsoas tendinopathy includes retraining muscle imbalances with strengthening and stretching exercises. If these fail to provide relief, corticosteroid injections may be used.

Another treatment called saline hydrodissection can relieve stress around the tendon by injecting fluids that both cushion and release trapped tissues.

In extreme cases, a surgery called a tendon release may be considered but only when all other options have failed. The surgical release of the iliopsoas tendon involves the severing of the tendon to reduce pain and improve the range of motion.

Rehabilitation

Core muscle exercises are central to the rehabilitation of iliacus muscle injuries. The iliopsoas is an integral component of the core muscle group and can benefit from stretching and strengthening exercises like:

• Lunge stretches
• Thomas (knee-to-chest) stretches
• Straight leg raises
• Standing hip flexion with resistance bands

Since the function of the iliopsoas is to flex and rotate the hip joint, certain yoga poses can also help. These include variations on the bridge pose that encourage hip flexion.

A Word From Verywell

Exercising and activities that keep you moving and active can improve your quality of life. Your iliacus muscles are integral in these pursuits. Always remember to warm up before doing any exercise to release and flex your tight muscles to avoid any strains or pains.

When you bend, dance, sit, or even take a leisurely walk, you know that your iliacus muscles and the other iliopsoas are working together to produce needed stability and range of motion.