[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Spine](https://durgical.com/en/anatomy/region/spine/) › L4 nerve root [Nervous system](https://durgical.com/en/anatomy/system/nervous-system/) · [Spine](https://durgical.com/en/anatomy/region/spine/) # L4 nerve root The L4 nerve root leaves the [spine](https://durgical.com/en/anatomy/region/spine/) through the L4-L5 opening; it helps straighten the knee and gives the knee-jerk reflex. Official name: L4 [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=spine&select=l4_root&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The L4 nerve root, leaving the spine through the L4-L5 opening. ## What it does Helps straighten the knee (quadriceps), gives the knee-jerk reflex, and feeling over the inner shin. ## Key points - ISNCSCI key muscle: ankle dorsiflexors ([tibialis anterior](https://durgical.com/en/anatomy/tibialis-anterior-muscle/)); key sensory point: medial malleolus - Pain runs from the low back to the front of the thigh, across the knee to the inner shin; the patellar reflex is reduced - The femoral stretch test, not the straight-leg raise, is the tension sign for the upper lumbar roots (L2–L4) ## Key facts **Roots** L4 dorsal and ventral roots; exits the L4–L5 foramen; compressed by L3–L4 posterolateral herniation (or far-lateral L4–L5) **Moves** Quadriceps (knee extension); tibialis anterior (with L5); hip adductors; patellar reflex (L3–L4) **Feeling from** Medial leg and medial malleolus ## Relations **Course** Crosses behind the [L3–L4 disc](https://durgical.com/en/anatomy/l3-l4/) inside the dural sac (where a posterolateral herniation catches it), passes under the L4 pedicle and leaves the L4–L5 foramen to join the femoral and obturator nerves and the lumbosacral trunk **In front** The L4 vertebral body and, in the foramen, the [L4–L5 disc](https://durgical.com/en/anatomy/l4-l5/) **Behind** The L4–L5 facet joint and [ligamentum flavum](https://durgical.com/en/anatomy/ligamenta-flava/) **Lateral** The [psoas major](https://durgical.com/en/anatomy/psoas-major/), inside which the [lumbar plexus](https://durgical.com/en/anatomy/lumbar-plexus/) forms ## How to find it It cannot be felt. It leaves through the L4–L5 foramen, under the L4 pedicle; in the paraspinal (Wiltse) approach for a far-lateral disc it is found lateral to the pars interarticularis, between the L4 and L5 transverse processes. ## Examination - [Femoral nerve](https://durgical.com/en/anatomy/femoral-nerve/) stretch test: lying prone, the knee is bent and the hip extended; pain in the front of the thigh suggests L2–L4 root tension - Patellar reflex, with the Jendrassik manoeuvre (hooking the fingers and pulling) if it seems absent - Heel walking and resisted ankle dorsiflexion (L4 key muscle); repeated single-leg sit-to-stand shows mild quadriceps weakness - Pinprick at the medial malleolus (L4 key point) ## On imaging MRI is the test of choice. Axial T2 at L3–L4 shows a paracentral herniation pressing on the traversing L4 root in the lateral recess; at L4–L5 a foraminal or far-lateral herniation presses on it as the exiting root. Sagittal slices through the foramen show foraminal narrowing, often with disc loss or spondylolisthesis. Radiographs only show bony changes. ## Common problems - Pinched by an L3-L4 herniation or by a far-lateral L4-L5 herniation: pain in the front of the thigh and inner shin. ## How it is diagnosed Exam (straight-leg raise, [big toe](https://durgical.com/en/anatomy/great-toe/) and foot lift strength, feeling); MRI. ## Treatment - Most sciatica improves within weeks to months with activity, physical therapy, medicine or an epidural injection. - Severe, lasting pain or weakness: microdiscectomy. ## Clinical notes - L4 root vs femoral nerve: a femoral lesion spares the hip adductors ([obturator nerve](https://durgical.com/en/anatomy/obturator-nerve/)) and tibialis anterior and causes no back pain; an L4 root lesion can weaken both - Far-lateral L4–L5 herniation catches the exiting L4 root and its ganglion outside the canal, with intense pain; it is easy to miss without looking lateral to the foramen on MRI - Diabetic lumbosacral radiculoplexus neuropathy (diabetic amyotrophy) mimics an upper lumbar radiculopathy: severe thigh pain, wasting and weight loss ## Related conditions - [Lumbar Disc Herniation](https://durgical.com/en/conditions/lumbar-disc-herniation/) ## Test yourself Think of the answer, then tap the question to see it. ## Which disc herniations compress the L4 nerve root? A posterolateral L3–L4 herniation, or a far-lateral L4–L5 herniation that catches the exiting L4 root outside the canal. ## Which reflex is reduced with an L4 radiculopathy? The patellar (knee-jerk) reflex (L3–L4), with pain from the front of the thigh to the inner shin. ## Which tension test is used for the L2–L4 roots instead of the straight-leg raise? The femoral nerve stretch test: prone, knee bent and hip extended; pain in the front of the thigh suggests L2–L4 root tension. ## How is an L4 root lesion told apart from a femoral nerve lesion? A femoral lesion spares the hip adductors (obturator nerve) and tibialis anterior and causes no back pain; an L4 root lesion can weaken both. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/l4/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** radix nervi spinalis L4 TA2 6489 **Official Spanish (DeCS)** Raíz L4 DeCS D013126 **English (TA2)** L4 **Also called** spinal nerves L1-L5 ## Related - [L3–L4 disc](https://durgical.com/en/anatomy/l3-l4/) - [Cauda equina](https://durgical.com/en/anatomy/cauda-equina/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=13510&filter=ths_termall&q=Ra%C3%ADces%20Nerviosas%20Espinales); [Anatomy, Skin, Dermatomes](https://www.ncbi.nlm.nih.gov/books/NBK535401/); [Neuroanatomy, Spinal Nerves](https://www.ncbi.nlm.nih.gov/books/NBK542218/). ## **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/l4/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/l4/