Kim Goodsell was running along a mountain trail when her left ankle began turning inward, unbidden. A few weeks later she started having trouble lifting her feet properly near the end of her runs, and her toes would scuff the ground. Her back started to ache, and then her joints too.

This was in 2002, and Kim, then 44 years old, was already an accomplished endurance athlete. She cycled, ran, climbed and skied through the Rockies for hours every day, and was a veteran of Ironman triathlons. She’d always been the strong one in her family. When she was four, she would let her teenage uncles stand on her stomach as a party trick. In high school, she was an accomplished