The Knee Jerk Reflex Quiz

• Knee jerk reflex (patellar reflex) is a test of the integrity of the femoral nerve and the L2-L4 spinal cord segments.
• When the patella is struck below the knee by a reflex hammer, it initiates an action potential in a specialized structure called a muscle spindle located within the quadriceps.
• This action potential travels to the L2, L3, and L4 nerve roots of the spinal cord via a sensory axon (femoral nerve) which chemically communicates with the motor nerve.
• The motor nerve (femoral nerve) carries stimuli back to the quadriceps muscle that make this muscle contract, leading to extension of the lower leg at the knee.
• The sensory input from the quadriceps also activates local interneurons that release inhibitory stimuli onto motor neurons of antagonist muscles, blocking their stimulation (in this case, the hamstring muscles).
• The relaxation of the opposing muscle facilitates (by not opposing) the extension of the lower leg.
• The reflex is routinely tested during a physical examination by having the person sit with the legs dangling.
• A firm strike on the ligament with a reflex hammer usually causes the leg to extend.
• Diminution or absence of the patellar tendon reflex may result from any lesion that interrupts the innervation of the quadriceps (e.g. peripheral nerve disease).
• Clinical correlation I is related to the knee jerk reflex (patellar reflex).

Test your knowledge of the knee jerk reflex with our quiz! Learn about the anatomy and physiology behind this important reflex and how it is tested during a physical examination. Discover the clinical correlations of the reflex and what can cause its diminution or absence. This quiz is perfect for medical students, healthcare professionals, or anyone interested in learning about the knee jerk reflex.