The quadriceps reflex is a medical term referring to the involuntary contraction of the quadriceps muscle when the patellar tendon is struck. It is also commonly known as the knee jerk reflex or patellar reflex. Other synonyms for this reflex include the monosynaptic reflex, deep tendon reflex or stretch reflex. Some medical professionals may also use terms such as myotatic reflex or muscle stretch reflex. Regardless of the name used, the quadriceps reflex is an essential diagnostic tool used in medical settings to assess the function of the nervous system and muscle strength in the lower extremities.