Describe the innervation of the lower extremity.
The lower extremity is innervated by the lumbar
plexus and the sciatic plexus.
The lumbar plexus consists of six nerves:
The upper part consists of three nerves:
ilioinguinal, genitofemoral, and iliohypogastric. These nerves supply parts of
the anterior abdominal wall, buttocks, and perineum. The lower part consists of
three nerves: femoral, lateral cutaneous nerve of the thigh, and obtu-rator.
The femoral is the main nerve of concern in a total knee arthroplasty. It
supplies innervation to the anterior
It continues as the
saphenous nerve below the knee and provides sen-sory innervation to the medial
aspect of the leg in this region. The lateral femoral cutaneous nerve provides
sensory innervation to the lateral aspect of the thigh, and the obturator nerve
provides innervation to the adduc-tors of the thigh and sensory innervation to
the medial aspect of the thigh.
The sciatic plexus consists of the sciatic and
the posterior cutaneous nerves of the thigh. The sciatic nerve provides
innervation to the hamstring muscles. At the popliteal fossa the sciatic nerve
splits into the common peroneal and posterior tibial nerves, which together
provide all the motor innervation to the leg below the knee and sensory
innervation to this area except for the medial part of the leg below the knee,
which is provided by the saphenous nerve. The posterior cutaneous nerve
provides sensory innerva-tion to the posterior aspect of the thigh.