Give a stream of consciousness and then the final answer. The term knee-jerk was recorded by Sir Michael Foster in his Textbook of physiology in 1877: "Striking the tendon below the patella gives rise to a sudden extension of the leg, known as the knee-jerk."

Answer this question: state the type of stimulus that would cause a knee jerk reflex to occur?
This is the relevant information: The term knee-jerk was recorded by Sir Michael Foster in his Textbook of physiology in 1877: "Striking the tendon below the patella gives rise to a sudden extension of the leg, known as the knee-jerk."
So, the final answer is Striking the tendon below the patella.