EE WAS EXITING CAT 216B SKID LOADER. HE STEPPED OUT OF MACHINE TO GROUND ON RIGHT LEG. BEFORE LEFT LEG REACHED GROUND HIS RIGHT KNEE CAP AREA POPPED CAUSING PAIN & FELL TO GROUND. DID NOT SEEK MEDICAL ATTENTION UNTIL FOLLOWING MORNING WHERE DOCTOR PRESCRIBED MEDICATION AND KNEE BRACE WITH LIGHT DUTY RESTRICTIONS FOR 5 DAYS.