The Anatomy of the Iliacus Muscle

Hip Flexor That Flexes and Rotates the Thigh Bone

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Nestled into the top part of the pelvic bone, the iliacus muscle extends all the way from your lowest rib to your thigh bone. When you bend, run, walk, sit, or dance, the iliacus muscle works together with the other muscles in your hip joint to keep you moving smoothly and without pain.


The iliacus muscle is part of a complex muscle system in the hip area that can function on its own or with other muscles. This flat, triangle-shaped muscle fits into the curved surface (called the iliac fossa) of the highest and largest pelvic bone, called the ilium or sometimes the iliac bone.

The Iliacus muscle starts on the upper two-thirds of the iliac fossa, and another part of this muscle is attached to the iliac crest, the top portion of the pelvic bone. The iliacus muscle interacts with the bundles of the abdominal muscle between your lowest rib and the top of your pelvis (quadratus lumborum muscle).

It extends on to the base of the tail bone (sacrum), in front of the upper and lower anterior iliac spines, and on the front capsule (a bunch of three ligaments) of the hip joint. The iliacus muscle continues down through the pelvis and attaches to the small piece of bone (lesser trochanter) that is attached to your femur (upper thigh bone).

The iliacus muscle is part of a major trio of muscles in each hip joint also known as the iliopsoas—the iliacus muscle, the psoas major muscle, and the psoas minor muscle, that work together when you are walking, running and standing after sitting.

The femoral nerve enervates this trio so that it can perform the motor functions needed to flex the thigh at the hip joint and stabilize the hip joint.


The iliacus muscle has many functions:

  • Flex and rotates the thigh bone (femur)
  • Helps to maintain proper body posture
  • Strong hip flexor (when working with the psoas muscle)
  • Adds to the down and forward tilt of the pelvis
  • Helps in bending the trunk of the body forward
  • In action constantly during walking
  • Helps control side-bending

Associated Conditions

Sedentary people or those who exercise without stretching first can shorten the iliacus muscle and cause problems, including:

  • Painful, tender, or stiff areas in the muscle (also called trigger points)
  • Reduced blood flow to the muscle (Iliacus ischemia)
  • Imbalanced hips, causing knee, hip, or back pain
  • Pain in the lower back, groin, hips, upper thigh

The terms Iliopsoas syndrome or psoas syndrome generally describe conditions that affect the iliopsoas muscles. Conditions such as liopsoas tendinitis, snapping hip syndrome, and iliopsoas bursitis typically affect gymnasts, dancers, track-and-field participants and others who repeatedly use movements that flex the hips.

Iliopsoas Bursitis

Iliopsoas bursitis is an inflammatory response in the liquid sac (bursa) between the muscles, ligaments, and joints located under the iliopsoas muscle, a group of two muscles located toward the front of the inner hip.

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 can experience pain because of the pressure on the ligaments, joints, and muscles. People with different forms of arthritis can also be affected.

Early treatment can help to avoid the condition from progressing. When you start to feel pain in this area, temporarily stop the exercise or activity that could have caused it. Mild cases of Iliopsoas bursitis can be treated at home with rest, icing, and over-the-counter anti-inflammatory medications. Stretching can be used to relieve tightness.

In more severe cases, some choices for treatment can include:

  • Physical therapy
  • Anti-inflammatory medications
  • Corticosteroid injection into the bursa
  • Antibiotics, if infection is present
  • Walking aids (such as a cane) to relieve pressure

But for the most part, rest and self-pampering can improve symptoms and help the healing process. If you experience joint pain, fever, chills, warm, red skin, or feeling sick, call your healthcare provider, as these symptoms may indicate an infection.

Iliopsoas Tendinopathy

Iliopsoas tendinopathy is another condition that affects the iliacus and psoas muscles. This condition, experienced by dancers who repeatedly flex and hyperextend their hip muscles can result in hip and groin pain that gets worse with kicking or hip rotation. You may even be able to hear an audible snapping sound.

Treatment for iliopsoas tendinopathy includes retraining muscle imbalances with targeted and strengthening stretching therapies. If these therapies are unsuccessful, ultrasound guided injections into the iliopsoas tendon bursa (which is filled with a thin layer of fluid) or saline peritenon hydrodissection (injecting fluid around a painful tendon, freeing it from neighboring structures) may be recommended.

Only in extreme cases should hip arthroscopy be considered unless all other treatment has failed.


Keeping active can help fend off issues related to the iliacus muscle. The type of stretching and bending associated with yoga can release tightness in the iliopsoas trio of muscles. The psoas location, attached to the spine and inner thigh and connected to the upper and lower body, is an integral component of the body’s “core.”

Since the function of the iliopsoas is to flex and rotate the hip joint, certain yoga poses like the supine knee to the chest pose, variations on supported bridge poses, and pelvic tilt poses that encourage hip flexion may help to release tight muscles after a long day of sitting or workouts that affect these muscles.

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 the needed stability and range of motion needed to get you back home again.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2.  Physiopedia. Iliacus.

  3. Siccardi MA, Tariq MA, Valle C. Anatomy, bony pelvis and lower limb, psoas major. StatPearls.

  4. Teach Me Anatomy, The femoral nerve.

  5. Physiopedia. Iliopsoas bursitis.

  6. Davenport KL. The professional dancer’s hip. In: Performing Arts Medicine. Ed. Lauren E. Elson. Elsevier, 2019, Pages 77-87, ISBN 9780323581820

  7. Yogateket. Essential yoga body parts. Hip flexor/psoas and yoga.

  8.  Yoga International. 8 poses for iliopsoas release.

By Mali Schantz-Feld
Mali Schantz-Feld is a medical journalist with over 25 years of experience covering a wide range of health, medicine, and dental topics.