What nerve root is tested by the patellar reflex?

The patellar reflex, commonly known as the knee-jerk reaction, is an important test to evaluate the integrity of the knee extensor muscles and associated nerve pathways. The primary nerve root involved in this reflex is L4. When the patellar tendon is tapped, it sends signals to the spinal cord through sensory neurons, primarily connected to the L4 nerve root.

In response, the spinal cord activates motor neurons that signal the quadriceps muscle to contract, effectuating the reflex movement of the leg extending at the knee. The involvement of the L4 nerve root in the patellar reflex is well established in neuroanatomy and clinical assessments, which is why understanding this connection is crucial for medical examiners and healthcare professionals during neurological examinations.