TRAVELLING ON INTERSTATE WHEN WHEN FRONT-END OF VEHICLE BEGAN TO VIBRATE. MOMENTS AFTER THE VIBRATION, THE CAR VEERED HARD RIGHT ON ITS OWN. UNABLE TO REGAIN CONTROL OF VEHICLE, AS STEERING WHEEL SEEMED AS IT WAS "LOCKED" IN A HARD-RIGHT ENABLING POSITION. THIS MALFUNCTION CAUSED THE DRIVER TO HIT A RETAINING WALL AT APPROX 55MPH, CAUSING BODILY INJURY. INSPECTION REVEALED A FAULTY/FAILED STEERING KNUCKLE, WHICH HAD COMPLETELY FAILED/SNAPPED. CAR CONSIDERED A TOTAL, AFTER INCIDENT.