PATHOLOGY

Detailed explanation-1: -Jerking of the knee when hit below the knee cap is a type of simple reflex. Simple reflexes are the type of reflex that is found in an organism starting from birth and are also called inborn or inherited reflexes.

Detailed explanation-2: -The patellar reflex, also called the knee reflex or knee-jerk, is a stretch reflex which tests the L2, L3, and L4 segments of the spinal cord. Many animals, most significantly humans, have been seen to have the patellar reflex, including dogs, cats, horses, and other mammalian species.