Kruisinga worked as an otolaryngologist and internist physician at the University Medical Center Groningen and the Medical Center Leeuwarden from January 1955 until 1 September 1962 and worked as an inspector for the Health Care Inspectorate of the Ministry of Social Affairs and Health in Friesland from 1 April 1960 until 1 September 1962.

After the election of 1967 Kruisinga was appointed as State Secretary for Social Affairs and Health in the Cabinet De Jong, taking office on 18 April 1967.

After the election of 1972 Kruisinga returned as a Member of the House of Representatives, taking office on 19 December 1972 but he was still serving in the cabinet and because of dualism customs in the constitutional convention of Dutch politics he couldn't serve a dual mandate he subsequently resigned as State Secretary on 20 March 1973.

Incumbent Deputy Prime Minister Dries van Agt of the Catholic People's Party was choose as the first Leader of the Christian Democratic Appeal and became the Lijsttrekker for the election of 1977.

On 4 March 1978 just three months after taking office Kruisinga resigned after he disagreed with the cabinets decision to not publicly condemn the United States for further developing the Neutron bomb.

Following the end of his active political career, Kruisinga occupied numerous seats as a nonprofit director for supervisory boards for several international non-governmental organizations and research institutes (Netherlands Cancer Institute, Netherlands Red Cross, Foundation KiKa, Stichting Max Havelaar, Society for the Advancement of Science, Medicine and Surgery and the Royal Dutch Medical Association).