The knee jerk reflex generally involves two neurons. The knee jerk reflex is a simple reflex that involves two neurons, a sensory neuron and a motor neuron. Nerve regulation is mainly controlled by reflexes, and the neural pathway from reception to response to action is called a reflex arc, so the knee jerk reflex generally involves two neurons. The knee-jerk reflex involves a rapid tap on the knee joint with a percussion hammer while the knee is semi-flexed and the lower leg is naturally drooping. This passes through the motor neurons and causes a contraction of the quadriceps muscle, which in turn causes the lower leg to kick forward rapidly. The nerve center of the knee-jerk reflex is a low-level nerve center located in the gray matter of the spinal cord. When the knee-jerk reflex is completed, it passes through the sensory neurons to the brain and produces the sensation of the knee joint being knocked. The knee-jerk reflex is usually composed of two neurons. If neuronopathy occurs, it can cause joint pain and make walking difficult. If uncomfortable symptoms, should seek medical treatment in time, at the same time, patients should maintain good living habits, not to stay up all night, light diet, avoid spicy and stimulating food.