Dr. Johnston received his medical degree at the University of Alberta in 2001 and completed his residency in orthopaedic surgery at the University of Calgary in 2006. Following his residency, he pursued subspecialty training in adult hip and knee reconstruction, hip joint preservation, and trauma. He completed fellowships in adult reconstruction and trauma at the University of Auckland in New Zealand in 2007 and adult reconstruction and hip preservation at the University of California, San Diego in 2008.

Dr. Johnston is an Assistant Clinical Professor at the University of Calgary and has practiced in Calgary since 2008. He is an attending orthopaedic surgeon at the Rockyview General Hospital and has acted as the head of the section of hip and knee reconstruction at the University of Calgary since 2014. His practice focuses on adult hip and knee reconstruction and hip preservation, including hip arthroscopy.

Dr. Johnston is active in the research activities of the Division of Orthopaedics at the University of Calgary and has published in a number of peer reviewed journals. He has held a number of peer reviewed grants and is reviewer for multiple journals including the Journal of Bone and Joint Surgery.