Unstoppable

If anyone understands the phrase "tough luck," it's Harrison. As a foster kid in a cruel home, he knows his dream of one day playing for the NFL is a longshot.
Then, Harrison's luck seems to change. He is brought into a new home with kind, loving parents - his new dad is even a football coach. Harrison's big build and his incredible determination quickly make him a star running back on the junior high school team. On the field, he's practically unstoppable.
But Harrison's good luck can't last forever. After a small football injury causes more pain than it should, Harrison undergoes a series of tests. It's discovered that he has a cancerous tumor on his knee that must be removed. Harrison goes to sleep in the hospital, and when he wakes up, his leg from the knee down is gone.
At first, Harrison is devastated. But with the help of his father's amputee friend from the military, and inspired by a fellow chemo patient at the hospital, Harrison rallies through a rigorous training program to prove himself unstoppable, not just as a player, but as a person.