Snapshot A 27-year-old woman gives birth to a healthy baby boy. She had an uncomplicated vaginal delivery and was placed in obstetric stirrups during the delivery. Soon after the birth, she complains of numbness and weakness in her right foot. On exam, she has decreased sensation to light touch along the dorsum of her foot including in the first webspace. Ankle dorsiflexion is 3/5 and ankle plantarflexion is 5/5. She walks with a steppage gait. (A compression neuropathy of the common peroneal nerve) Overview Introduction Clinically relevant nerves to the lower extremity hip/thigh motor login to view 5 more bullets sensory login to view 3 more bullets leg/foot motor login to view 4 more bullets sensory login to view 5 more bullets Obturator Nerve (L2-L4) Motor innervation hip adduction adductor magnus, longus, and brevis gracilis Sensory innervation medial thigh Terminal branches none Injury causes rare anterior hip dislocation motor deficit impaired hip adduction sensory deficit sensory loss over medial thigh Femoral Nerve (L2-L4) Motor innervation hip flexion iliacus sartorius rectus femoris (part of the quadriceps femoris) knee extension quadriceps femoris login to view 2 more bullets Sensory innervation anteromedial thigh medial leg and foot (via the saphenous nerve) Terminal branches saphenous nerve Injury causes trauma login to view 1 more bullet compression login to view 1 more bullet iatrogenic login to view 1 more bullet motor deficit impaired hip flexion impaired knee extension sensory deficit sensory loss over the anteromedial thigh sensory loss over the medial leg Sciatic Nerve (L4-S3) Motor innervation knee flexion hamstrings login to view 3 more bullets Sensory innervation no direct sensory innervation dorsum of the foot and anterolateral leg (via superficial peroneal nerve) plantar aspect of the foot (via tibial nerve) posterolateral leg (via sural nerve) Terminal branches common peroneal nerve tibial nerve Injury causes trauma login to view 1 more bullet entrapment login to view 1 more bullet iatrogenic login to view 1 more bullet motor deficit impaired knee flexion impaired ankle dorsiflexion, plantarflexion, inversion, and eversion sensory deficit sensory loss over dorsal and plantar surfaces of the foot sensory loss over the lateral leg Common Peroneal Nerve (L4-S2) Motor innervation knee flexion biceps femoris (short head) Sensory innervation lateral knee anterolateral leg and dorsum of foot (via superficial peroneal nerve) posterolateral leg (via sural nerve, which also receives innervation from the tibial nerve) Terminal branches deep peroneal nerve superficial peroneal nerve Injury causes compression login to view 3 more bullets trauma login to view 1 more bullet motor deficit impaired ankle and toe dorsiflexion login to view 2 more bullets impaired ankle eversion sensory deficit sensory loss over anterior and lateral leg sensory loss over dorsum of the foot including first webspace Deep Peroneal Nerve (L4-L5) Motor innervation ankle dorsiflexion tibialis anterior toe extension extensor digitorum longus extensor hallucis longus Sensory innervation first webspace Terminal branches none Injury causes compression login to view 1 more bullet trauma login to view 1 more bullet motor deficit impaired ankle dorsiflexion login to view 1 more bullet impaired ankle inversion login to view 1 more bullet sensory deficit sensory loss over first webspace Superficial Peroneal Nerve (L4-S1) Motor innervation ankle eversion peroneus longus and brevis Sensory innervation anterolateral leg dorsum of foot except for the first webspace Terminal branches none Injury causes trauma login to view 1 more bullet motor deficit impaired ankle eversion sensory deficit sensory loss over the anterolateral leg sensory loss over the dorsum of the foot Tibial Nerve (L4-S3) Motor innervation ankle plantarflexion gastrocnemius-soleus complex ankle inversion tibialis posterior toe flexion flexor digitorum longus flexor hallucis longus Sensory innervation plantar aspect of the foot (via medial and lateral plantar nerves) posterolateral leg (via sural nerve, which also receives innervation from the common peroneal nerve) Terminal branches medial and lateral plantar nerves Injury causes trauma login to view 1 more bullet motor deficit impaired ankle plantarflexion impaired ankle inversion login to view 1 more bullet impaired toe flexion sensory deficit sensory loss over plantar aspect of the foot Superior Gluteal Nerve (L4-S1) Motor innervation hip abduction gluteus medius and minimus tensor fascia latae Sensory innervation none Terminal branches none Injury causes posterior hip dislocation injection to upper medial gluteal region motor deficit impaired hip abduction login to view 13 more bullets Trendelenburg test login to view 3 more bullets Trendelenburg gait login to view 1 more bullet Trendelenburg test patient is asked to lift one foot off the ground and to stand on one foot normally, the gluteus medius and gluteus minimus muscles contract to abduct the hip and prevent it from tipping to the unsupported side in a patient with an SGN injury, the pelvis will tip to the unsupported side due to impaired hip abduction Trendelenburg gait a patient with an SGN injury will lean away from the unsupported side when walking to indirectly raise the pelvis in order to allow their leg to clear the ground sensory deficit none Trendelenburg test patient is asked to lift one foot off the ground and to stand on one foot normally, the gluteus medius and gluteus minimus muscles contract to abduct the hip and prevent it from tipping to the unsupported side in a patient with an SGN injury, the pelvis will tip to the unsupported side due to impaired hip abduction Trendelenburg gait a patient with an SGN injury will lean away from the unsupported side when walking to indirectly raise the pelvis in order to allow their leg to clear the ground Inferior Gluteal Nerve (L5-S2) Motor innervation hip extension gluteus maximus Sensory innervation none Terminal branches none Injury cause rare hip arthroplasty motor deficit impaired hip extension login to view 1 more bullet sensory deficit none Lateral Femoral Cutaneous Nerve (L2-L3) Motor innervation none Sensory innervation anterolateral thigh Terminal branches none Injury cause compression as the nerve passes under the inguinal ligament (meralgia paresthetica) login to view 3 more bullets motor deficit none sensory deficit sensory loss, numbness, and paresthesias over the anterolateral thigh Sensory Innervation to the Foot The foot has multiple nerves carrying sensory input Identifying areas of sensory loss can aid in the localization of specific nerve lesions Localization lateral foot sural nerve login to view 1 more bullet medial foot saphenous nerve login to view 1 more bullet dorsal aspect of the foot superficial peroneal nerve login to view 1 more bullet first webspace deep peroneal nerve login to view 1 more bullet plantar aspect of the foot tibial nerve (via lateral plantar, medial plantar, and calcaneal nerves) login to view 1 more bullet