What are the dermatomes of the lower extremities?

Updated: Oct 13, 2017
  • Author: Stephen Kishner, MD, MHA; Chief Editor: Thomas R Gest, PhD  more...
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Answer

Answer

Dermatomal distribution in the lower extremity has a spiral arrangement stemming from the rotation of the limb as an adaptation to the erect position during development (see the following image).

Dermatomes of the extremities. Dermatomes of the extremities.

NOTE: Pain due to pleurisy, peritonitis, or gallbladder disease can often be referred to the skin over the point of the shoulder, halfway down the lateral side of the deltoid muscle. This is because this area of skin is supplied by the supraclavicular nerves (C3 and C4), and the pain generated from pleurisy, peritonitis, and/or gallbladder disease is carried from the diaphragmatic pleura and peritoneum via afferent fibers of the phrenic nerve (C3-C5). [10]

Below, Table 4 describes the lower extremity dermatomes.

Table 4. Dermatomes of the Lower Extremity and Genitalia (Open Table in a new window)

Spinal Component

Skin Distribution

L1 dermatome

The skin over the back lateral to the L1 vertebra; wraps around the lower trunk/upper part of lower extremity to the hip girdle and the groin area

L2 dermatome

Anterior aspect of each thigh; the skin over the medial aspect of the mid thigh

L3 dermatome

Anterior aspect of each thigh; anterolateral thigh and continues down to the medial aspect of the knee and the medial aspect of the posterior lower leg, proximal to the medial malleolus

L4 dermatome

Posterolateral thigh and the anterior tibial area; it crosses the knee joint over the patella and also covers the skin over the medial malleolus and the medial aspect of the foot and the great toe

L5 dermatome

Posterolateral thigh (just inferior to L4 dermatome) and wraps around to lateral aspect of the anterior lower leg and dorsum of the foot; it crosses the knee joint on the lateral aspect of the knee; also covers the plantar aspect of the foot and the second through fourth toes

S1 dermatome

The heel, the lateral aspect of the foot, the lateral aspect of the posterior thigh, and most of the posterior lower leg

S2 dermatome

Most of the back of the thigh and a small area along the medial aspect of the posterior lower leg; the penis and scrotum

S3 dermatome

The medial aspect of the buttocks; perianal area; penis and scrotum

S4 dermatome

Skin over the perineal region (along with S5); perianal area and genitals

S5 dermatome

Skin over the perineal region (along with S4); the skin immediately at and adjacent to the anus


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