[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Lower limb](https://durgical.com/en/anatomy/region/lower-limb/) › Iliopsoas fascia [Muscular system](https://durgical.com/en/anatomy/system/muscular-system/) · [Lower limb](https://durgical.com/en/anatomy/region/lower-limb/) # Iliopsoas fascia The iliopsoas fascia is a thin, tough sheet covering the psoas and iliacus muscles inside the [pelvis](https://durgical.com/en/anatomy/region/pelvis/) and down into the groin. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=lower_limb&select=iliopsoas_fascia&side=r) Opens in the Durgical app, no sign-up needed. ## What it is A thin, tough sheet covering the psoas and iliacus muscles. A thickened part (the iliopectineal arch) divides the space under the inguinal ligament in two. ## What it does Wraps the hip flexor muscles and separates the femoral nerve from the femoral artery and vein at the groin. ## Key points - The iliopectineal arch splits the space under the inguinal ligament: muscular lacuna (iliopsoas, femoral nerve, lateral femoral cutaneous nerve) laterally, vascular lacuna (femoral artery, vein, canal) medially - The femoral nerve runs under the iliac fascia, outside the femoral sheath: the basis of the fascia iliaca block - A psoas abscess, for example from spinal tuberculosis (Pott disease), tracks down inside the sheath and can point in the groin below the inguinal ligament ## Key facts **Where** Covers psoas major and iliacus, from lumbar [spine](https://durgical.com/en/anatomy/region/spine/) and iliac fossa down beneath inguinal ligament **Attaches** Lumbar vertebrae, iliac crest and pelvic brim; forms posterior wall of femoral sheath **Function** Encloses iliopsoas; a psoas abscess can track under it into the thigh ## Relations **Above** Thickened as the medial arcuate ligament of the [diaphragm](https://durgical.com/en/anatomy/diaphragm/), over the upper [psoas major](https://durgical.com/en/anatomy/psoas-major/) **Superficial** Extraperitoneal fat and [peritoneum](https://durgical.com/en/anatomy/peritoneum/) in the [abdomen](https://durgical.com/en/anatomy/region/abdomen/); below the [inguinal ligament](https://durgical.com/en/anatomy/inguinal-ligament/) the [femoral artery](https://durgical.com/en/anatomy/femoral-artery/) and [femoral vein](https://durgical.com/en/anatomy/femoral-vein/) lie on it inside the femoral sheath **Deep** Psoas major and [iliacus](https://durgical.com/en/anatomy/iliacus-muscle/); the [lumbar plexus](https://durgical.com/en/anatomy/lumbar-plexus/) forms inside psoas, and the [femoral nerve](https://durgical.com/en/anatomy/femoral-nerve/) and [lateral femoral cutaneous nerve](https://durgical.com/en/anatomy/lateral-femoral-cutaneous-nerve/) run under the iliac part of the fascia **Below** Follows the iliopsoas under the inguinal ligament towards the lesser trochanter ## How to find it In the groin the femoral pulse marks the vascular lacuna; the femoral nerve lies just lateral to it, under the iliac fascia. On ultrasound the fascia is the bright line over iliacus, with the nerve beneath it lateral to the femoral artery. ## On imaging CT or MRI shows a psoas abscess or haematoma held within the fascial sheath, sometimes extending below the inguinal ligament into the thigh; ultrasound shows the fascia and the femoral nerve for regional blocks. ## Clinical notes - Fascia iliaca block: local anaesthetic spread under the fascia reaches the femoral and lateral femoral cutaneous nerves; widely used for pain relief in hip fractures - A psoas abscess may come from the spine or from the bowel (Crohn disease, appendicitis); the hip is held flexed and extension hurts (psoas sign) - A retroperitoneal haematoma, especially on anticoagulants, can collect under the fascia and compress the femoral nerve, causing quadriceps weakness and thigh numbness ## Anatomical variants - Psoas minor, whose tendon fans into the iliac fascia and the iliopubic eminence, is missing in a large share of people (around 40% in commonly quoted figures) ## Related conditions - [Spinal tuberculosis (Pott disease)](https://durgical.com/en/conditions/spinal-tuberculosis/) ## Test yourself Think of the answer, then tap the question to see it. ## How does the iliopectineal arch divide the space under the inguinal ligament? Into a lateral muscular lacuna (iliopsoas, femoral and lateral femoral cutaneous nerves) and a medial vascular lacuna (femoral artery, vein and canal). ## Why does the fascia iliaca block reach the femoral nerve but not the femoral vessels? The femoral nerve runs under the iliac fascia, outside the femoral sheath that holds the vessels. ## How can a psoas abscess from spinal tuberculosis reach the groin? It tracks down inside the iliopsoas fascial sheath and can point below the inguinal ligament. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/iliopsoas-fascia/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** fascia iliopsoae TA2 2386 **Official Spanish (DeCS)** Fascia del iliopsoas DeCS D005205 **English (TA2)** Iliopsoas fascia **Also called** fascia iliopsoas · fascia iliopsoatica ## Related - [Inguinal ligament](https://durgical.com/en/anatomy/inguinal-ligament/) - [Psoas major](https://durgical.com/en/anatomy/psoas-major/) - [Iliacus](https://durgical.com/en/anatomy/iliacus-muscle/) - [Femoral nerve](https://durgical.com/en/anatomy/femoral-nerve/) - [Femur](https://durgical.com/en/anatomy/femur/) - [Hip bone](https://durgical.com/en/anatomy/hip-bone/) - [Sacrum](https://durgical.com/en/anatomy/sacrum/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=5309); [Anatomy, Bony Pelvis and Lower Limb: Iliopsoas Muscle](https://www.ncbi.nlm.nih.gov/books/NBK531508/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/iliopsoas-fascia/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/iliopsoas-fascia/