National Board of Chiropractic Examiners (NBCE) Practice Test 2025 - Free Chiropractic Practice Questions and Study Guide

A herniation of the L4 disc primarily affects the nerve roots associated with the L4 spinal nerve, which has significant implications for muscle function and strength. The L4 nerve root is responsible for the innervation of several muscles in the lower extremity, particularly those involved in knee extension and ankle dorsiflexion.

The Extensor Hallucis Longus muscle, which is primarily innervated by the deep fibular (peroneal) nerve that has contributions from the L4 nerve root, plays a crucial role in extending the big toe and aiding in dorsiflexion of the foot. When the L4 disc herniates, it can impinge on the spinal nerves, leading to weakness in the Extensor Hallucis Longus due to disrupted nerve signals.

In contrast, while the quadriceps muscle is also affected by L4, it is primarily innervated by the femoral nerve, which includes contributions from L2-L4, but the strong relationship and predominant weakness that occurs with an L4 disc herniation are more closely observed with the Extensor Hallucis Longus. The hamstrings and tibialis anterior, while they may share some nerve root associations, are less directly impacted by an L4