Section 01 of 20
Introduction
Iliacus is a broad, triangular muscle that fills the iliac fossa on the inner surface of the pelvis. Its fibers converge and join the tendon of psoas major to form the iliopsoas tendon.
It lies deep in the abdominopelvic region, behind the abdominal contents, and can be reached only indirectly by careful, consented palpation.
Section 02 of 20
Origin
| Origin | Upper two-thirds of the iliac fossa, the inner lip of the iliac crest, the ala of the sacrum, and the anterior sacroiliac ligaments. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 03 of 20
Insertion
| Insertion | Lateral side of the psoas major tendon and the lesser trochanter of the femur, with some fibers to the shaft just below it. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 04 of 20
Actions
No dedicated action video is currently available. This movement is explained below and video will be added when verified source media becomes available.
| Primary action | Hip flexion. |
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| Secondary actions | Anterior pelvic tilt when the femur is fixed and weak lateral rotation. |
| Movement at the joint | Hip joint. |
| Heads / fiber groups | Single broad muscle; joins psoas major as the iliopsoas. |
| Functional examples | Walking and running (swinging the leg forward); climbing stairs; sitting up from lying; kicking. |
Hip flexion
Flexes the thigh at the hip, especially when lifting the leg against gravity.
Trunk flexion on the femur
When the femur is fixed, it tips the pelvis forward (anterior pelvic tilt) and helps bring the trunk toward the thigh.
Lateral rotation
May assist slight lateral rotation of the thigh.
Section 05 of 20
Nerve Innervation
| Nerve | Femoral nerve, roots L2–L3 (some sources include L4). |
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The femoral nerve runs in the groove between iliacus and psoas major. Hip flexion weakness, thigh numbness, or a knee that gives way may reflect nerve problems, not only muscle tightness.
Section 06 of 20
Blood Supply
| Blood | Iliac branch of the iliolumbar artery, with contributions from the deep circumflex iliac and femoral circumflex arteries. |
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Section 07 of 20
Pictures and Visual Anatomy
An anatomical image for this section will be added when verified source media becomes available.
Section 08 of 20
Functional Movement
Iliacus works with every step of walking and running as the leg swings forward, when climbing stairs, and when sitting up from lying down. Long periods of sitting keep it in a shortened position.
Section 09 of 20
Synergists and Antagonists
Synergists: psoas major (with iliacus as iliopsoas), rectus femoris, sartorius, pectineus, and tensor fasciae latae. Antagonists: gluteus maximus and the hamstrings (hip extension).
Section 10 of 20
Palpation and Location
Client position and technique
Palpation is indirect and needs clear consent and communication. Position the client supine with the knees bent and the abdomen relaxed. Contact the area just inside the anterior superior iliac spine and move slowly and gently inward and downward along the inner edge of the ilium, following the client's breathing and comfort.
Protect nearby structures
The abdominal cavity, femoral artery, femoral nerve, and inguinal lymph nodes lie nearby. Use slow, light pressure, stay lateral to the pulse, and stop at any pain, tingling, or unusual pulsation. Avoid the area entirely in pregnancy, after recent abdominal surgery, or with known aneurysm.
Section 11 of 20
Massage Therapy Relevance
Iliacus is commonly shortened by long periods of sitting. It can be associated with front-hip tightness, anterior pelvic tilt, and low back or hip discomfort, but many other structures cause similar symptoms.
Section 12 of 20
Dysfunction: What Happens When Movement Goes Wrong
Changes in how a muscle works can change how a joint moves. The points below describe possibilities that may be associated with altered muscle function; they are not diagnoses, and one muscle is never assumed to be the sole cause of a problem.
When the muscle is weak
Weakness may reduce the ability to lift the leg and may be associated with a shorter stride and more work by the rectus femoris and tensor fasciae latae.
When it is tight or shortened
Tightness may be associated with limited hip extension, anterior pelvic tilt, and front-hip or low back discomfort, especially after long periods of sitting.
When it is overused
Repeated hip flexion in running, kicking, and cycling may overload the muscle and tendon and may contribute to groin or front-hip pain.
When it is strained
A strain may cause front-hip or groin pain with resisted hip flexion; hip joint, hernia, and lumbar causes can look similar.
When it is inhibited or others compensate
Reduced activation may be associated with poor hip flexion control and more work by the rectus femoris and other flexors.
When it does not coordinate well with synergists and antagonists
Poor coordination with psoas major, the abdominals, and gluteus maximus may alter pelvic position and may be associated with low back or hip symptoms.
Section 13 of 20
Conditions, Pathologies, and Pain Relationships
Hip flexor tightness
A tight iliopsoas may limit hip extension and may be associated with anterior pelvic tilt and increased lumbar curve.
Iliacus tendinopathy or strain
Sprinting, kicking, and repeated hip flexion can strain the muscle or tendon and cause groin or front-hip pain.
Iliopsoas bursitis and snapping hip
A snapping sensation at the front of the hip may involve the iliopsoas tendon crossing the hip joint.
Differential considerations
Hip joint problems, hernia, femoral nerve entrapment, abdominal or pelvic conditions, and lumbar referral can all cause groin or front-hip symptoms.
Section 14 of 20
Example Clinical Relationship
An office worker who sits for many hours reports tightness at the front of the hip when standing up and an ache in the low back. Iliacus and psoas may be shortened, and the pattern may be associated with hip flexor tightness, but the hip joint, the lumbar spine, and abdominal causes can look similar. Gentle work on the anterior hip flexors may support comfort, while severe abdominal pain, a groin bulge, or new leg weakness needs referral.
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Massage and Treatment Approaches
For healthy, non-acute tissue, use secure draping and clear consent. Begin with light effleurage and gentle compression along the anterior thigh and hip flexors, and consider gentle hip mobilization and range-of-motion within comfort. Indirect abdominal work should be brief, light, and always guided by client feedback.
| Positioning | Supine with the knees bent and supported by a bolster, or side-lying with the top leg supported. |
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| Regional work | Consider the quadriceps, rectus femoris, tensor fasciae latae, sartorius, and lumbar region when assessment supports it. |
| Avoid | Deep pressure in the lower abdomen, over the femoral triangle, or near a pulse; anything that reproduces leg pain or tingling. |
Section 16 of 20
Precautions and Contraindications
Precautions and contraindications
- Pregnancy, recent abdominal or pelvic surgery, or known abdominal aortic aneurysm: do not perform deep abdominal work.
- Use caution with hernias, inflammatory bowel disease, or any abdominal pain of unknown cause.
- Use caution with anticoagulant use or easy bruising.
- Always obtain explicit consent and use secure draping for hip and groin area work.
Section 17 of 20
Red Flags and When to Refer
Red flags and referral
- Severe or worsening abdominal pain, fever, or a pulsating mass in the abdomen.
- Groin bulge, testicular pain, or blood in the urine.
- Sudden hip or groin pain after a fall, or inability to bear weight.
- New leg weakness, numbness in the thigh, or bladder or bowel changes.
Section 18 of 20
Study Summary
Attachments
Origin: iliac fossa. Insertion: psoas tendon and lesser trochanter.
Actions
Hip flexion; tips the pelvis forward when the femur is fixed.
Supply
Femoral nerve (L2–L3); iliac branch of the iliolumbar artery.
Section 19 of 20
Instructor Narration
Open narration transcript
Iliacus is the broad, fan-shaped muscle that lines the iliac fossa on the inside of the pelvis. It joins psoas major to form iliopsoas.
It arises from the upper two-thirds of the iliac fossa, the inner lip of the iliac crest, and the ala of the sacrum, and inserts on the psoas tendon and the lesser trochanter of the femur.
It flexes the hip and, when the femur is fixed, tips the pelvis forward. Psoas major, rectus femoris, sartorius, and pectineus help it, and gluteus maximus and the hamstrings oppose it.
The femoral nerve supplies it, from L2 to L3, and the iliac branch of the iliolumbar artery provides its blood.
Palpation is indirect. Obtain consent, place the client supine with the knees bent, and move slowly inward from the anterior superior iliac spine. Stay lateral to the femoral pulse and stop at any pain or tingling.
Hip flexor tightness, strain, snapping hip, hernia, and femoral nerve problems can overlap. Refer a pulsating abdominal mass, severe abdominal pain, groin bulge, new leg weakness, or bladder or bowel changes.
Remember: iliac fossa to the lesser trochanter, hip flexion, femoral nerve.
Section 20 of 20