Dr. Armstrong’s orthopaedic residency was done at the University of Toronto followed by a pediatric orthopaedic fellowship with Dr. Robert Salter at The Hospital for Sick Children in Toronto. Following his fellowship, in 1982, he joined the orthopaedic staff at The Hospital for Sick Children in Toronto. In 1991, he became Chief of Staff of Shriners Hospitals for Children Intermountain (Salt Lake City). In 2000, he was selected as Chief Medical Officer of the 22 Shriners Hospitals and moved to the Headquarters in Tampa. He began as the Chief Medical Officer for OrthoPediatrics, an orthopaedic device company in January of 2013 and retired from that at the end of March 2021. He began the Foundation for Advancing Pediatric Orthopaedics in 2018. In May of 2023, he was inducted into the Pediatric Orthopaedic Society of North America – Hall of Fame.