Knight was the son of William Knight of Newbury, and his wife Alice Worthington. In 1643 he commanded a troop of cavalry in the Earl of Manchester's regiment of horse. He was appointed to the New Model Army in 1645 as a captain in the cavalry regiment of Colonel Matthew Tomlinson. By 1647 he had become a major in the same regiment. He became aide-de-camp to General Monck. In about 1650, he purchased the estate of Langold, Yorkshire from Thomas Burton, as a residence for his wife near her relations. He was appointed a Deputy Lieutenant for the West Riding of Yorkshire in 1653. In 1659 he represented Sutherland Ross and Cromarty in the Third Protectorate Parliament.
In 1660, Knight was elected Member of Parliament for Morpeth in the Convention Parliament. He was knighted on the Restoration. In 1662 he purchased the manor of Letwell, Yorkshire. In June 1667 at the time of military emergency he was captain of a company of non-regimental horse raised from the border of Nottinghamshire and Yorkshire. The company marched to Yarmouth in case there was a Dutch invasion, but was disbanded on 16 August 1667. He became lieutenant-colonel of the Duke of Buckingham's Regiment of Foot on 12 May 1673 and in 1675 he bought the Manor of Warsop in Nottinghamshire.
Knight died at Firbeck in April 1691 and was buried there on 23 April.
Knight married firstly on 23 June 1646, Faith Dickinson, daughter of the Rev. William Dickinson, vicar of Rotherham. He married secondly, the widow of John Rolleston of Sokeholme.