From the Research
The L2 and L3 nerve roots are primarily responsible for hip flexion, as they innervate the iliopsoas muscle complex, which is the main hip flexor in the human body. The femoral nerve, which arises from the lumbar plexus (primarily L2-L4 nerve roots), plays a crucial role in hip flexion. The iliopsoas muscle complex, composed of the iliacus, psoas major, and psoas minor muscles, is the primary hip flexor, as noted in a study published in 2020 1. Additionally, the rectus femoris muscle, which is part of the quadriceps group and also contributes to hip flexion, receives innervation from the femoral nerve. Other muscles that assist with hip flexion include the sartorius and pectineus, which are also innervated by the femoral nerve. This arrangement allows for coordinated movement during activities like walking, climbing stairs, and rising from a seated position. Understanding this nerve root distribution is important for clinical assessment of hip flexion weakness, which may indicate pathology affecting the upper lumbar nerve roots or the femoral nerve itself.
Some studies have investigated the correlation between muscle mass and quality around the hip and of psoas muscles at L3 level using unenhanced CT scans 2, and the anatomical study of the lumbar segmental arteries in relation to the oblique lateral interbody fusion approach 3. However, these studies do not directly impact the primary nerve roots responsible for hip flexion.
Key points to consider:
- The femoral nerve is primarily responsible for hip flexion
- The L2 and L3 nerve roots contribute most significantly to this function
- The iliopsoas muscle complex is the main hip flexor in the human body
- Other muscles, such as the rectus femoris, sartorius, and pectineus, also contribute to hip flexion and are innervated by the femoral nerve.