The patella hammer is a medical instrument used to test the deep tendon reflexes, which help indicate the health of your overall nervous system. The reflex hammer elicits the classic “knee jerk” response, among other tests.
Striking of the with a just below the stretches the in the . This produces a signal which travels back to the spinal cord and synapses (without interneurons) at the level of L3 or L4 in the spinal cord, completely independent of higher centres. From there, an conducts an efferent impulse back to the , triggering contraction.contraction, coordinated with the relaxation of the antagonistic flexor hamstring muscle causes the leg to kick.There is a latency of around 18 between stretch of the patellar tendon and the beginning of contraction of the quadriceps femoris muscle. This is a reflex of which helps maintain and , allowing to keep one's balance with little effort or conscious thought.