westphal's sign westphal's sign westphal's sign is the clinical correlate of the absence or decrease of patellar reflex or knee jerk. patellar reflex or knee jerk is a kind of deep or stretch reflex where an application of a stimulus to the patellar tendon such as strike by a solid object or hammer caused the leg to extend due to such stimulus causes the quadriceps femoris muscle to contract. westphal's signpatellar tendon reflex arcdifferential diagnosisperipheral nerve disease, motor cortex lesion it is named for karl friedrich otto westphal (1833-1890). associated conditions westphal's sign has a clinical significance used in determining neurodisorders or diseases such as: receptor damage, peripheral nerve disease, involving the dorsal(sensory) columns of the spinal cord and cerebellar lesions lesions present within the motor cortex of the brain or the pyramidal tracts which it combined with muscular spasms complete interruption of sensory and/or motor impulse transmission in the femoral nerve