MADRID: Real Madrid star Kaka, who has been ruled out through injury for three to four months, said he had a problem with his left knee even before the World Cup.

"This knee has been bothering me for quite some time. But I didn`t know that it was so serious. I was the first to be surprised..," the Brazilian playmaker told the Spanish sports newspaper AS published Saturday.

"I was always being treated for a groin strain and I was told that it could cause muscular imbalance in other parts, but I didn`t know it was so serious."

Real Madrid announced on Thursday that the 28-year-old had undergone a successful operation on his knee in Antwerp, Belgium and would be out of action for three to four months. He returned to Madrid on Friday.

He told AS he had felt the pain in the knee "even before the World Cup. I always told them in Madrid that it was bothering me a bit but as I was being treated for the groin strain it seemed that it was just a muscle imbalance that was not becoming as serious as it now appears to be."

Kaka, signed from AC Milan for 65 million euros in the summer of 2009, told AS he was devastated by the injury.

"I have to say that I`m not the bad guy. I need people to believe in me. For me it`s a nightmare to be out for another four months.

Brazil were eliminated by the Netherlands in the quarter-finals of the World Cup, in which Kaka failed to shine.

Brazil team doctor Jose Luiz Runco admitted last month that Kaka was not properly fit for the tournament and wouldn`t have played at a lesser event.

BDST: 1656HRS, August 7, 2010