Dawn Comstock might know more about high-school sports injuries than anybody else. A researcher at the Center for Injury Research and Policy at Nationwide Children’s Hospital in Columbus, Ohio, Comstock publishes the nation’s foremost annual report on injuries to American high-school athletes. She tracks them all: concussions, sprains, fractures and very rarely something worse.

Since 2000, at least two other football players have suffered in-game injuries that led to leg amputations not unlike Rainey’s. But limb loss hardly registers among football mishaps. In the last decade, the U.S. Consumer Product Safety Commission, which monitors football injuries in a representative sample of American hospitals, has recorded just eight amputations at any level of the sport — seven of fingers, one of a thumb — which is too few to calculate a national estimate.

By comparison, over the same time frame, the C.P.S.C. estimates that there have been roughly one million football-related fractures. Even paralysis appears to be more common. In the last decade, the Annual Survey of Catastrophic Football Injuries, published by Frederick O. Mueller at the University of North Carolina, has documented 94 cervical-cord injuries with paralysis — more than 10 times the number of reported amputations. “Amputations in football are incredibly rare,” Comstock told me. “And a leg amputation? I can’t even tell you how rare it is, to be honest with you. . . . We just don’t see it happen.”

Last fall, Rainey knew better than anyone just how unusual his case was. Laid up for months, he had plenty of time, perhaps too much, to think. Insomnia only made matters worse. At night, while his family slept, Rainey killed time by surfing the Internet and watching television. Sometimes he read stories about himself and even relived his injury. “I got the scrimmage film in the fall, and I watched that a lot,” he told me. “I don’t know why I did, but I couldn’t stop watching it.”

For a while, Rainey, like others, believed it would be his final football play; among other problems was the fact that he dropped 60 pounds after his injury. But well before he received his prosthetic leg in late December, he was considering a comeback. His parents supported him; failure, they told him, was not trying at all. Before winter was over, he was becoming impatient with his physical therapists and the slow pace of his recovery. “We weren’t really doing anything,” he said, “but just walking in circles.”

David Lawrence works as a physical therapist, in a low-slung, redbrick office complex in Richmond, about a 90-minute drive from the Raineys’ house in Charlottesville. He’s 50 and beginning to gray around the temples but exudes youthful enthusiasm. He’s seen enough to expect the impossible — or at least to encourage it — from patients who are missing limbs.

Lawrence once coached the national disabled volleyball team. He still works with one of the players: Joe Sullivan, a below-the-knee amputee who became a prosthetist and shares office space with Lawrence. In late March, they met together with Rainey for the first time.