Knee Jerk

The Knee jerk reflex is observed during a neurological exam by striking the knees directly with a hammer when the patient's leg is relaxing. Striking the patellar ligament with a reflex hammer just below the patella stretches the muscle spindle in the quadriceps muscle. After the tap of a hammer, the leg is normally extended once and comes to rest.



Simulation Type

Condition, Using interactive animation

Gender Specific

No, Common for both genders

Condition Simulated


     Slight reflex(Normal)-rated as 2+

     Super-normal (hyper-reflexic) rated as 3+

     Clonus: Repetitive shortening of the muscle after a single stimulation rated as 4+

     No evidence of contraction rated as 0 (Westphal's sign)


     The user can select the position of the patient to be tested.The testing can be done in sitting position and in supine position of the patient.

     The system will display patient's leg hanging downwards and can move freely, click on the ‘Strike’ button and a toggle button to change the legs.

     Hit "Strike" button to strike on patient’s knee with a hammer.

     An animation showing patient’s leg will be played.

     Note the rate of patient’s leg movement.

     Patient's response rate will will be indicated in a response box.