The on-loan Sunderland midfielder deflected Sam Deering's 67th-minute cross into his own net less than a minute after Wycombe's Matt McClure had cancelled out Jamie Cureton's opener to hand Cheltenham their first league win in four games.
Cheltenham had started the better of the two sides and should have taken the lead a quarter of an hour in when Byron Harrison badly scuffed his shot wide from Deering's cross after Josh Scowen had slipped.
But Wycombe gradually got into the game with Dean Morgan denied by the legs of Scott Brown after a free-flowing passing move.
Jamie Cureton handed the visitors a 56th-minute lead when he turned in Jason Taylor's cross and the game opened up after that, especially after McClure's introduction.
It was the young striker who produced a measured finish after Knott's ball had fallen kindly to him. However Deering's cross seconds later hit Knott to condemn Wycombe to a fifth game without a win.