The femoral nerve is a major nerve in the leg, playing an important role in movement and sensation. It contributes significantly to a person’s ability to walk, run, and maintain balance. As part of the peripheral nervous system, it transmits signals enabling motor and sensory functions.
Femoral Nerve Origin and Course
The femoral nerve originates from the lumbar plexus, a network of nerves located in the lower spine, specifically from the L2, L3, and L4 spinal nerves. The nerve emerges from the side of the psoas major muscle and then descends between the iliacus and psoas major muscles. It passes deep to the inguinal ligament, a strong band of tissue in the groin, to enter the anterior compartment of the thigh. Within the thigh, it is positioned lateral to the femoral artery and then divides into several branches.
Key Muscles of the Thigh
The femoral nerve provides innervation to several muscles in the anterior thigh, which are primarily responsible for hip flexion and knee extension. The iliacus muscle, located in the pelvis, receives branches from the femoral nerve before it passes under the inguinal ligament. Once in the thigh, the nerve supplies the sartorius muscle, which runs diagonally across the front of the thigh. The pectineus muscle, found in the upper and inner thigh, also receives primary innervation from the femoral nerve.
The quadriceps femoris group, a large set of four muscles on the front of the thigh, is innervated by the femoral nerve. This group includes the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. These muscles are important for leg movements and stability.
Movement and Sensation Controlled
The muscles innervated by the femoral nerve enable several movements of the lower limb. The iliacus, sartorius, and rectus femoris contribute to hip flexion, which is lifting the knee towards the torso. The quadriceps femoris muscles are the primary extensors of the knee, allowing for straightening of the leg. The sartorius also aids in knee flexion, abduction, and lateral rotation of the hip, such as crossing one’s legs.
Beyond motor control, the femoral nerve provides sensory innervation to the skin of the anterior and medial thigh. The saphenous nerve, a terminal branch, extends down the medial side of the lower leg and foot, providing sensation to these regions. The femoral nerve also sends branches to the hip and knee joints, contributing to proprioception, which is the body’s sense of its position in space.
Effects of Femoral Nerve Injury
Damage to the femoral nerve can lead to symptoms primarily affecting movement and sensation in the lower limb. Individuals might experience weakness or difficulty with hip flexion, making activities like climbing stairs challenging. Weakness or paralysis of knee extension can cause the knee to buckle, leading to falls. This weakness stems from impaired function of the quadriceps femoris muscles.
Sensory disturbances are common following femoral nerve injury. These can include numbness, tingling, or a reduced ability to feel touch, pain, or temperature in the anterior and medial thigh. Sensory loss may also extend to the medial side of the lower leg and foot due to saphenous nerve involvement. The combination of motor weakness and sensory changes can impact a person’s mobility and daily activities.