In some cases, this answer is obvious. For instance, a knee injury requiring surgery will most likely be considered a serious personal injury. I say ‘most likely’ because ultimately it is up to a judge or jury to determine if something is a serious personal injury. Remember, you are usually trying to recover money from an insurance carrier. Insurance carriers decide whether they want to make offers in limited tort cases based upon their feelings/guesses about whether a judge or jury would consider it a serious injury.
I can tell you that I monitor cases all around the city of Philadelphia, and that I have been doing this for over thirty years. I have seen cases where judges or juries found that a broken leg, broken arm, or herniated disk were not serious personal injuries, and gave nothing for pain and suffering.
I can assure you that if you injure your neck or back, have physical therapy for six months, and then are discharged by your doctor as being mostly improved, you DO NOT have a serious personal injury.