In 2013, an Australian man a few months shy of turning 60 decided to walk the Camino de Santiago – an 800km pilgrimage trail across the top of Spain. He had no known religion, and absolutely no idea why he felt so deeply compelled to do this torturous walk. But compelled, he was. He completed the walk, battling a “triumvirate of pain” - a knee that he later discovered lacked an...