The Newcastle fly-half, injured against Worcester on Friday, revealed the extent of his latest crisis in his column in The Times.
He said: "I've gone past the stage of saying 'Why me... why does it always happen?'
"I know some people will start thinking about what that means regarding the autumn international season.
"I guess it does not augur well but, to be honest, thoughts of England are miles away.
"I've started to come to terms with my situation. I accept the injuries more quickly and rather than wasting mental energy feeling frustrated I'm instead thinking 'What can I do to cut down the rehab time.'"
He added: "The injury is exactly the same as the old knee injury except it's the right knee this time. It's a grade two partial medial ligament tear. It took me nine weeks to come back from the last one.
"I heard quite a rigorous pop [when it happened], a noise I recognised from when I'd injured my left knee. When I stood up I had that same loose feeling around the joint so I knew pretty much immediately what had happened.
"I knew I couldn't play on, I was just keen to get off the field and get it iced."