All of us can be prone to particular injuries and illness to various extents. In an enormously physical game like football, the former can be due to many factors but the genetics along with individual pain thresholds creates various degrees of recovery and future prevention. I have personally severely sprained my ankles numerous times including breaking one playing basketball and for most of my older life am prone to taking a tumble if stepping on a ridged sidewalk or uneven surface. Pro players have the best doctors and trainers but sometimes their bodies just don't recover as quickly and like concussions, one can lead to another and another, etc.
"Injury prone" is indeed a condition that is difficult and sometimes impossible to overcome until eventually a player resigns from putting themselves in the recurring situation. The money makes it worth it until the body finally disagrees and then one spends the rest of their life in some degree of pain and danger of recurrence.
