The Anatomy of the Iliopsoas Muscle

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The iliopsoas muscle is a major mover of your hip joint. It's formed by the joining of three muscles: the iliacus muscle, the psoas major muscle, and the psoas minor muscle. These muscles work together as the iliopsoas to flex your hip and to stabilize your hip and lower back during activities such as walking, running, and rising from a chair. Your body has two iliopsoas muscles; one is on the left, and one is on the right. Injury to the iliopsoas may cause hip pain and limited mobility.

Anatomy

The iliopsoas consists of three distinct muscles. They are usually grouped together due to their common attachment point on your femur (thigh bone).

  • Iliacus muscle: This iliacus arises from the inner part of your pelvic bowl on the upper two-thirds of the iliac fossa and the upper lip of the iliac crest. If you imagine your pelvis as a bowl, the iliacus originates from the inner surface on one side of the bowl. The iliacus muscle then courses down through your pelvis and attaches to the lesser trochanter of your femur.
  • Psoas major muscle: This muscle originates at the front surfaces of the vertebral bodies, intervertebral discs, and transverse processes of your spine at thoracic level 12 through lumbar level five. It then courses down through your pelvis and joins psoas minor and iliacus to insert on the lesser trochanter of your femur.
  • Psoas minor muscle: The psoas minor arises from the vertebral bodies and discs of thoracic 12 and lumbar level one. It then inserts along the psoas major in an area called the pectineal line and iliac fascia.

All three muscles arise from different areas of your lumbar spine and pelvic brim, but all three join to inert near the inner portion of your thigh bone near the front of your hip. There is a fluid-filled bursa that lies near the iliopsoas muscle that helps it glide and slide over the front of your hip during movement.

The iliacus muscle gets nerve supply from the femoral nerve at lumbar level two, three, and four. The psoas major is innervated by the lumbar plexus at lumbar level two, three, and four. The psoas minor receives nerve supply from lumbar level one.

The iliopsoas muscle gets blood supply from the iliolumbar artery that arises from the internal iliac artery.

Anatomical Variations

The psoas minor has been shown to be absent in 40% of the population. Other variations include muscles originating from different points or the lumbar plexus (the network of nerves stemming from the lumbar region) entering the psoas major muscle, leading to symptoms of nerve entrapment, otherwise known as a pinched nerve.

Function

Since the iliopsoas muscle arises from different places in your pelvic area and lumbar spine, it functions in different ways. The main action of the iliopsoas is to flex your hip. The means that it bends your hip towards your body, as in the action of marching. It's considered the major flexor of your hip.

If your iliopsoas muscle contracts on only one side of your body, it works to assist in lateral flexion, or side-bending, of your lower spine. When you have one foot on the ground and the other in the air, as occurs with walking, the iliopsoas contracts to help stabilize your pelvis, hip, and lumbar spine.

The psoas major portion of the iliopsoas flexes your hip, but it also assists your rectus abdominus muscle in flexing your lumbar spine. This occurs when you are lying on your back and go to sit up. The psoas major contracts and pulls your lumbar spine into flexion to help you rise.

Some professionals also have shown the psoas muscles assist with bending your spine backwards into extension. This is in direct opposition to flexion, so the question arises of how the psoas can both extend and flex your spine. This is often referred to as the "psoas paradox."

Your psoas muscle acts as a lumbar spine flexor when your body is in certain positions, and it can assist other muscles to pull your low back into extension when your body is in other positions. The contribution of the psoas during extension has been shown to be minor, but the psoas paradox remains an interesting caveat of the function of the muscle.

Associated Conditions

There are many different problems that may involve your iliopsoas. These conditions may cause pain, weakness, and difficulty with basic tasks such as walking, running, and rising up from a supine position. While these problems are prevalent in athletes, they can affect anyone. Conditions that may affect your iliopsoas may include:

  • Iliopsoas tendonitis: This occurs when the tendons that attach the iliopsoas to your femur become irritated and inflamed. Symptoms of iliopsoas tendonitis may include pain in the front of your hip when flexing your hip, pain with stretching your hip into extension, and difficulty with running. Iliopsoas tendonitis occurs as a result of overuse, and muscular imbalance or tightness and weakness of neighboring muscles may contribute to the condition.
  • Iliopsoas bursitis: If the small, fluid-filled sac in the front of your iliopsoas becomes irritated, bursitis may result. This irritation of the bursa can result in hip pain and difficulty with flexing and extending your hip. Usually, iliopsoas bursitis does not hurt when forcefully contracting your hip. Rather, the pain occurs when your hip is stretched and the iliopsoas muscle presses into the bursa.
  • Snapping hip syndrome: Often referred to as "dancer's hip," snapping hip syndrome occurs when there is a popping or snapping sensation in the front of your hip while moving it. It's usually painless, but it can be rather annoying to constantly feel a snapping sensation while moving. Snapping hip is often caused by tightness of the iliopsoas muscle, allowing it to rub and snap around other bony or ligamentous structures in your hip. In a study of elite ballet dancers, researchers found 91% with snapping hip and 58% of those reported pain from it.
  • Weakness of iliopsoas due to lumbar injury: If you have a low back condition such as herniated discs or lumbar facet arthritis, your femoral nerve may become compressed. This may cause pain in the front of your thigh, and your iliopsoas muscle may become weak—and even decrease in size—as a result. This weakness due to lumbar radiculopathy may make it difficult to walk and rise from a supine position normally. If the weakness is severe, immediate attention may be necessary to get pressure off your nerve and to restore normal nerve function to the muscle.
  • Spasm of iliopsoas: Occasionally people with low back pain or hip pain experience iliopsoas spasm. This causes a tight feeling in the front of your hip and makes extending your hip backward difficult. Iliopsoas spasm may be caused by repetitive strain or overuse. Spasm of your iliopsoas may also occur as the result of nerve injury due to a neurological condition such as multiple sclerosis or after a stroke.

While many of the conditions that affect the iliopsoas may cause pain and limited mobility, other conditions that cause hip pain may be at play. A hip labrum tear can cause pain in the front of your hip, and a condition called femoroacetabular impingement (FAI) can make flexing and extending your hip painful. Hip arthritis can cause limited mobility with your hip joint. These conditions may or may not affect the iliopsoas directly.

If you are experiencing hip pain or difficulty walking, you should visit your physician right away. They can help diagnose your condition and can guide you to the correct treatment.

Rehabilitation

After visiting with your physician to determine the cause of hip pain and limited mobility, you may benefit from working with a physical therapist (PT) to help you treat your iliopsoas condition. Your PT may recommend various treatments for your iliopsoas. These may include:

Rest

If you're experiencing iliopsoas irritation due to overuse, resting it for a few days may be recommended. Stop any activity that's causing hip pain. Rest is usually recommended, and then starting gentle stretches and strengthening exercises is recommended.

Stretching

If your iliopsoas muscle is tight, stretches may be prescribed. To stretch your iliopsoas:

  1. Get into a half-kneeling position as if you were genuflecting. The knee on the ground should be the side you are stretching.
  2. Maintain upright posture, and slowly slide forward, bringing your hip into extension and stretching your psoas.
  3. Hold the stretch for 30 seconds, and then relax.
  4. Repeat three times.

You can also stretch your hip iliopsoas while lying on your back on a bed or massage table:

  1. Simply slide to one edge of the bed, and then allow your leg and thigh to fall towards the floor. As your hip moves into extension, your iliopsoas will be stretched.
  2. Hold this position for 30 seconds, and then relax.

Strengthening

If your iliopsoas muscle is weak, strengthening exercises may be done. Simple straight leg raises on your back or resisted seated marching may be recommended. Resistance can be added with cuff weights or with a resistance band.

You can also strengthen your iliopsoas while standing. Simply use a resistance loop that is tied to a stable object. Place the loop around your ankle, maintain upright posture, and flex your straight leg forward. Hold the flexed position for three seconds, and then slowly release.

Strengthening exercises can be done for 15 to 20 repetitions. Two or three sets may be done once a day. Stop if you feel any increasing pain while doing the exercise.

Low Back Exercise

If a pinched nerve is causing iliopsoas weakness, getting pressure off your nerve may be recommended. Often this is accomplished by performing lumbar stretches like press ups or supine lumbar flexion. Sometimes, lumbar side-gliding is helpful. Check with your PT to determine the correct exercise for your specific lumbar condition.

Heat or Ice

Pain in the front of your hip due to iliopsoas injury may be managed by applying ice or heat to the affected area. Usually, ice is used during the initial acute phase of injury and is applied for 15 to 20 minutes several times a day. After a few days of ice, heat can be used for 15 minutes several times a day.

Be careful; heat or ice may cause skin irritation or burns, so be sure to use a covering over any hot pack or ice bag. Your PT can help determine if you should use heat or ice and can be sure it is applied safely.

Psoas Massage

There's some debate in the physical therapy community as to whether psoas massage is effective or necessary. The procedure, often called a psoas release, is difficult to do, and it may be painful.

Psoas massage is performed by having someone place their hands on your lower abdomen and slowly working through your superficial muscles to the deep area where your iliopsoas is located. Once the iliopsoas is palpated, gentle massage can be done, or a static press on the muscle may be done. After a few minutes of massage, the psoas is released.

Many physical therapists debate that it's impossible to be sure that the hands of the therapist performing the massage are actually touching the psoas. Plus, psoas massage is painful for the patient and has not been shown to provide any superior outcomes when compared to stretching or strengthening.

Before starting any treatment for your iliopsoas injury, visit with your physician and PT to ensure you are doing the correct things for your specific condition.

A Word From Verywell

The iliopsoas muscle is a major hip flexor that also helps to move your spine. The three muscles of the group—the iliacus, the psoas major, and the psoas minor—arise from different areas of your pelvis and lumbar spine to form a common attachment in your hip. Knowing the anatomy of this muscle can help you make good choices in caring for an iliopsoas injury.

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Article Sources

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