Vidic suffered cruciate ligament damage in his right knee in United's Champions League group game against Basle in December 2011 which sidelined him for the remainder of that season.
Then, after playing in the Red Devils' opening five matches of the current campaign, the Serbian centre-back underwent surgery on the same knee in September.
He returned to action in December and has featured in 10 of United's last 16 fixtures in all competitions, starting nine of those.
And after sitting out the 1-1 Champions League last-16 first leg draw at Real Madrid on February 13, over the last few days Vidic has completed back-to-back starts - in victories over Reading in the FA Cup and QPR in the Premier League - for the second time since his September operation.
Regarding his fitness, the 31-year-old said: "I had problems with my knee and I was so long without football.
"It is difficult now we are playing Wednesday-Saturday-Wednesday.
"I have had to think whether it is good for me to play or not. Sometimes I will get a reaction and sometimes I won't. This is normal.
"Since I came back I have had to say if I can get through the two or three months. Then I will be fine.
"It is not a long-term thing. It is the normal procedure after the kind of op I had."
United's 2-0 win at QPR on Saturday ensured they remain firmly on course for the league title, with the gap between them and second-placed Manchester City currently standing at 12 points with 11 top-flight games left to play each.
Someone who has been a part of all the Red Devils' previous 12 triumphant Premier League campaigns is Ryan Giggs, who netted the team's second goal at Loftus Road. Even at 39, the midfielder remains a key player for United and Vidic has paid tribute to Giggs.
"Ryan is very professional and is such an example for the young players," Vidic said.
"They see how you have to treat yourself and educate yourself in football to be a great player. Of course he has the quality and ability as well. He is a great example of how to be professional and to play at the top for so long. We have quite a few players like that. Rio (Ferdinand) is the same. He is a committed professional the same as Paul Scholes."