The patellar reflex can be defined as the kicking movement of the lower leg which occurs with a sudden twitch when the patellar tendon of a person is tapped. This patellar tendon is present below a person's kneecap. This reflex happens only when the leg is bended. It is impossible for patellar reflex to occur if the leg is straight as the quadriceps muscles are already contracted and a sudden kicking movement of the leg in such state could not be elicited. The patellar reflex protects the quadriceps from stretching too much.
