 Greenhow worked in all areas of surgery and had a particular interest in obstetrics and gynaecology; in 1845, he controversially published detailed accounts regarding his views on the gynaecological status of Harriet Martineau, who was both his patient and sister-in-law.Greenhow was a pioneer in the establishment of the University of Durham and in 1855 was a lecturer at the Newcastle-Upon-Tyne's medical college, in connection with Durham University.He and Sir John Fife founded what would become the Newcastle University Medical School.