In personal injury and Mass Tort cases, most states have a 2 year Statute of Limitations, which typically begins to run from the date of the injury or when the injured party knew or should have know that the injury was cause by the defective drug or medical device.
This is a method by which the courts and by states legislatures to put a hard time limit on cases so that folks cannot bring cases for injuries that happened years ago, otherwise there would be no end to litigation.