From the Research
The L2, L3, and L4 nerve roots, specifically the L3 and L4 nerve roots, are responsible for sensation in the quadriceps muscle and knee area. The femoral nerve, which arises from the lumbar plexus, supplies motor function to the quadriceps muscle group and provides sensory innervation via its terminal branches, including the anterior cutaneous branches and the saphenous nerve 1. This anatomical arrangement explains why patients with L3-L4 radiculopathy or femoral nerve injury often experience numbness, tingling, or pain in the anterior thigh and knee region, as well as potential weakness in knee extension, which is the primary function of the quadriceps muscle. Some of the key evidence supporting this includes a study from 2021 that demonstrated the feasibility of sartorius-to-quadriceps nerve transfers in a cadaveric study, highlighting the importance of the femoral nerve in quadriceps function 2. Additionally, a study from 2024 reviewed the anatomy and clinical features of femoral and obturator neuropathies, emphasizing the role of the L2, L3, and L4 spinal nerve roots in the formation of the femoral nerve 1. Understanding this innervation pattern is crucial for accurately diagnosing and localizing neurological problems affecting the lower limb. Key points to consider include:
- The femoral nerve arises from the lumbar plexus, primarily from the L2-L4 nerve roots
- The L3 and L4 nerve roots provide the majority of sensory innervation to the anterior thigh and knee
- The femoral nerve supplies motor function to the quadriceps muscle group and provides sensory innervation via its terminal branches
- Patients with L3-L4 radiculopathy or femoral nerve injury may experience numbness, tingling, or pain in the anterior thigh and knee region, as well as potential weakness in knee extension.