After years of chronic pain, Spokane resident Carrie Day had two knee replacements this year. She’s 40, part of the fastest growing U.S. demographic for total knee replacements.

Denise Olson danced at her daughter’s wedding. That might not sound like a profound accomplishment, but it was a moment she could only dream of a few months earlier. Arthritis had worn away so much of the cartilage in Olson’s right knee that it was just bone grinding on bone.