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 obturator nerve femoral nerve sciatic nerve superior gluteal nerve inferior gluteal nerve sensory lateral femoral cutaneous nerve obturator nerve femoral nerve leg/foot motor tibial nerve common peroneal deep peroneal nerve superficial peroneal nerve sensory sural nerve saphenous nerve deep peroneal nerve superficial peroneal nerve tibial nerve 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 rectus femoris vastus medialis, intermedius, and lateralis Sensory innervation anteromedial thigh medial leg and foot (via the saphenous nerve) Terminal branches saphenous nerve Injury causes trauma penetrating pelvic injury compression prolonged hip flexion (e.g., lithotomy position) iatrogenic pelvic, abdominal, or spinal surgery 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 semimembranosus semitendinosus biceps femoris (long head) 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 lumbar intervertebral disc herniation entrapment piriformis syndrome iatrogenic hip surgery 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 obstetric or anesthesia stirrups lying on side during anesthesia without appropriate padding tight plaster cast of leg trauma fracture of fibular neck motor deficit impaired ankle and toe dorsiflexion presents as a foot drop patient will compensate with exaggerated hip and knee flexion (steppage gait) 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 tight laces or ski boots trauma anterior ankle trauma motor deficit impaired ankle dorsiflexion presents as a foot drop with a steppage gait impaired ankle inversion tibialis posterior can still invert the foot 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 fracture of the fibular diaphysis 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 posterior knee dislocation motor deficit impaired ankle plantarflexion impaired ankle inversion tibialis anterior can still invert the foot 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 presents with a positive Trendelenburg test and a Trendelenburg gait 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 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 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 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 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 presents with difficulty climbing stairs, stepping onto a bus, and arising from a chair 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) pregnancy tight clothing obesity 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 receives branches from the tibial nerve and common peroneal nerve medial foot saphenous nerve terminal branch of the femoral nerve dorsal aspect of the foot superficial peroneal nerve terminal branch of the common peroneal nerve first webspace deep peroneal nerve terminal branch of the common peroneal nerve plantar aspect of the foot tibial nerve (via lateral plantar, medial plantar, and calcaneal nerves) terminal branch of the sciatic nerve