"I had the operation nearly two weeks ago and things are looking good. Hopefully, I could be back even sooner than the six weeks," Richards told the Manchester Evening News.
"The operation was something that couldn't be avoided. I played in the derby at Old Trafford with it hurting and in the second half picked up an ankle knock as well so I was a wreck by the end of the game.
"After the Everton match the knee was swollen like a balloon and I couldn't carry on really. The medical advice was to get it done before the end of the season and that is what I did. It is for the best in the long term.
"I hate missing games, especially at such a crucial time but I will be giving it 100 per cent to be fit as soon as I possibly can. I will be back and I will be back with a bang!"