The L5 dermatome runs down the outer (lateral) side of the lower leg and across the top of the foot to the big toe and the first three toes. It is the area most commonly affected by sciatica from an L4-L5 disc. The key sensory point is on the dorsum of the foot.
| Nerve root | L5 |
|---|---|
| Area | Lateral lower leg, dorsum of the foot and the first three toes including the big toe |
| How to test | Light touch and pinprick are compared side to side at the ISNCSCI key sensory point: on the dorsum of the foot at the third metatarsophalangeal joint. |
| Nerve Supply | Superficial fibular nerve; Deep fibular nerve; Lateral sural cutaneous nerve |
Carries touch, pain and temperature sensation from this strip of skin to the spinal cord through the L5 dorsal root.
L5 radiculopathy gives pain down the back or side of the leg to the top of the foot, with weak big toe extension, weak hip abduction and often a normal knee and ankle reflex. Common fibular nerve palsy at the fibular head is the main mimic, but it spares hip abduction and ankle inversion, which an L5 root lesion usually weakens. Dermatome maps differ between sources (Foerster, Keegan and Garrett, and modern evidence-based maps disagree), and neighbouring dermatomes overlap, so borders are approximate.
Compression of the L5 root, most often by an L4-L5 disc herniation or lateral recess stenosis, causing sciatica to the top of the foot and foot drop in severe cases.
Compression at the fibular neck causes foot drop and numbness on the top of the foot but spares hip abduction and foot inversion.
This website uses cookies to enhance your experience. Some are essential for site functionality, while others help us analyze and improve your usage experience. Please review your options and make your choice.
If you are under 16 years old, please ensure that you have received consent from your parent or guardian for any non-essential cookies.
Your privacy is important to us. You can adjust your cookie settings at any time. For more information about how we use data, please read our privacy policy. You may change your preferences at any time by clicking on the settings button below.
Note that if you choose to disable some types of cookies, it may impact your experience of the site and the services we are able to offer.
Some required resources have been blocked, which can affect third-party services and may cause the site to not function properly.
This website uses cookies to enhance your browsing experience and ensure the site functions properly. By continuing to use this site, you acknowledge and accept our use of cookies.
