Clues to solve the paradox have emerged from an unlikely place. Jose Luis Pelaez/Stone via Getty ImagesIn early December 2021, I was seeing a physical therapist for a shoulder injury. During one of my visits, the therapist was alternating between me and another patient on an adjacent bed, who had a knee replacement. While the therapist worked on the other patient’s leg, stretching it and bending the knee, I eavesdropped on their conversation. The patient was in pain, anxious to complete the hard