Johnston emigrated to Australia from Scotland in 1949. He took up a position as a physiotherapist at the Rehabilitation Services and Spinal Unit of Royal Perth Hospital in Shenton Park. In 1954, he introduced sport as part of rehabilitation activities.The man who started it all (21 March 1972). The Broadcaster (Fairfield, NSW : 1935 - 1978), p. 5. Retrieved 8 November 2018, from http://nla.gov.au/nla.news-article224497189 That year, he had around 5 inpatient paraplegics. In 1970, in recognition of his expertise, he was awarded a Commonwealth Scholarship to study sport as part of rehabilitation. By 1972, he had acquired six assistants as part of his staff.  Around that time, Johnston and his staff treated approximately 40 in-patient paraplegics, while also serving  variable number of paraplegics as outpatients.  Johnston and his staff treated around 43 quadriplegics at the same time. He retired in February 1977 from Royal Perth Hospital and moved to Malaysia.
