No, the Word knight is a common noun, a Word for any knight of any kind.
A proper noun is the name of a specific person, place, thing, or a title; for example:
- "Richard Knight's Treasure!: The True Story of His Extraordinary Quest for Captain Kidd's Cache" by Glenys Roberts
- Knight Street, Dallas, TX or Knight Street, Warwick, RI
- Knight Capital Group, Inc. (financial services), Jersey City, NJ
- Knights Inn Downtown San Francisco, CA
- "Knights of the Round Table" (1954) movie with Robert Taylor, Ava Gardner
