The decision comes after Knight’s husband Terry Biddlecombe – himself a three-times champion jockey – suffered a stroke seven months ago.
She admitted the choice was an emotional one to make, but nonetheless the right decision.
“I feel that I can’t go on training since Terry’s stroke,” she said.
She will nonetheless continue to pursue her equestrian interests. Knight breeds and shows Connemaras.
The 65-year-old has trained more than 700 winners, including legendary three-times Gold Cup winner Best Mate.