The 28 year-old made it seven wins from seven fights, all inside the scheduled distance, after dispatching the Russian in the eighth round to become the first fighter to stop Knyazev through his 13 contests.
Usyk has made steady progress since entering the paid ranks on the back of a stellar career with the head guard and vest in November 2013 and seems destined to be mixing it at the very top level in the cruiserweight division before too long.
Also on the bill, former European middleweight champion Max Bursak warmed up for his shot at the vacant IBO title at the higher 168lb limit in June by blasting out Chris Hermann in just one round. Hermann was floored three times in the opening session as Bursak sensed the end early on and eventually claimed victory towards the end of the round.
With the victory, Bursak, 30, pushes his record to 31-3-1 with his 14th knockout and will now travel to Australia in the summer in his bid to pick up the green and gold belt against the undefeated and highly-rated Zac Dunn.