They say bad things happen to good people. But what if they happen twice? You suffer an injury, and while on the mend you have an accident. Or, you have a medical condition made worse by an accident. Now what? A person with a medical condition that is worsened by another person's negligence can hold the other person responsible for any aggravation caused by the accident. The negligent party, or defendant in a law suit, can be held responsible for any aggravation of a prior injury or condition that is factually caused by the accident. In any law suit, the person who has been injured, the plaintiff, bears the burden of proof. They must prove that a defendant's negligent conduct caused damages. Therefore, the question for a court, or an insurance company in considering settlement, is: "Was the defendant's negligence a cause of harm that would not have occurred without the accident?" So, for example, take a middle aged person with degenerative disc disease, who may have had a backache here and there, but never enough to warrant going to a doctor. They are sitting waiting for a red light when someone babbling on the cell phone plows into the back of the car, destroying the car and sending the driver to the hospital. Fortunately nothing is broken, but the driver is in severe pain and requires months of physical therapy or other treatment before they can be considered close to normal. In every case like this ever, the insurance claims adjuster is going to point to the hospital x-rays. "Nothing is broken. Look, the person had degenerative disc disease." Insurance company attorneys blow these x-rays up and point them out with laser pointers to the jury: "Look, this person already had back problems." Generally, these issues are easy. The injured person must prove that the defendant's conduct caused the plaintiff's damages. The question is: "Was the defendant's negligent conduct in slamming into the back of the car a factual cause in bringing about the plaintiff's injuries?" So, a reasonable jury, judge or claims adjuster in this case will pay in recognition that the injured person might have had degenerative issues before, but never required treatment, so all of the post accident treatment, medical bills and even the potential likelihood for possible surgery in the future are a direct result of the accident and should be paid through this case. The reason for this is that negligent conduct is a factual cause of harm when the harm would not have occurred absent the conduct. An act is a factual cause of an outcome if, in the absence of the act, the outcome would not have occurred.