COLORADO SPRINGS — The last thing Morgan Stickney remembers from before her lower leg was amputated is lying on a hospital gurney waiting for the anesthesia to take hold. With a debilitating fear racing through her mind, she asked her surgeon to hold her hand. They talked about swimming until she passed out.

“It’s the last moment I had with two legs,” she said. “I was in the pool, the most happy place for me.”

Five years earlier, Stickney had dreams of becoming an Olympian. At 15, she ranked in the top 20 nationally in the mile, a freestyle event, and was a rising star out of Bedford, N.H.

But by the time she was wheeled into surgery last May, her Olympic dream had long since vanished. A relatively minor foot injury in 2013 had dragged her down a rabbit hole of five surgeries, numerous examinations and untold theories, none of which relieved — or even explained — the constant, excruciating pain that left her unable to walk by day and then, cruelly, stabbed her awake at night.