He started as a schoolmaster, but painting was his hobby, and he subsequently devoted himself to it. In 1861 he had his first picture hung at the Royal Academy. He was essentially an open-air painter, constantly going on sketching tours in the most picturesque spots of England, and all his pictures were painted out of doors. He died at Dover on 2 January 1908.
The Chantrey trustees bought Knight's "December's Bareness Everywhere" for the nation in February 1908. Most of his best pictures had passed into the collection of Mr Iceton of Putney (including "White Walls of Old England" and "Hereford Cathedral"), Mr Walter Briggs of Burley in Wharfedale (especially "Pinner"), and Mr SM Phillips of Wrotham (especially two watercolours of Richmond Bridge).