Tiger Woods rated his marathon US Open victory at Torrey Pines as one of the g reatest of his career but already there is concern the world No1 could have done himself serious harm.

The 32-year-old American claimed his 14th major title at the first extra hole after an 18- hole play- off against veteran Rocco Mediate ended in stalemate.

But for someone who underwent arthroscopic surgery to remove damaged cartilage in his left knee only nine weeks ago, playing 91 holes under intense pressure in five days may lead to long-term repercussions.

Clearly wincing after several of his crunching drives, Woods only made it to the end with the use of painkillers and liberal icing of his knee.

He will now have the injury scanned, with one possible outcome being the need for microfracture surgery - a technique in which fractures in adjacent bones help stimulate the growth of new cartilage.

The pay-off should be a strong knee that would see Woods through to the end of the competitive career. But the cost is an initial prolonged lay-off like the one that kept 2005 Ashes cricket hero Simon Jones out of the defence of the trophy in Australia two years later.

Woods is already doubtful about his chances of playing in the Open Championship at Royal Birkdale next month and, if surgery is requires, he could miss the Ryder Cup in September.

Meanwhile, the enormity of Woods's latest triumph, which takes him to within four of the record 18 majors won by Jack Nicklaus, was underlined by his coach Hank Haney.

He said: "Tiger hadn't walked nine holes until the Saturday before the event. He had been hitting no more than a bucket of 50 balls a day. And then he comes out and plays like that. How does he do it?"

Extraordinary talent helps. But sheer grit and determination also played their part.

Cheered on a huge gallery that followed the play-off despite it being a workday Monday in southern California-Woods was never going to concede to that knee.

"I wasn't going to bag it," he said. "I think everyone knows me well enough that, it's not in my nature. I don't know how to do that.

"It helped to have that energy from all the fans, because there were times when it stung quite a bit. I had a couple of zingers. But it's nice to have that energy out there, and you're trying to feed off it somehow. You always try to use everything to your advantage, anyway, trying to be a rationalist, it's part of playing our sport.

"I try to do the best I could. It's been sore every day. It's been sore for a while. I just dealt with it.

"I knew I could walk, it was just going to be a little bit on the slow side. But I was just trying to get through this week. Everyone plays with nick-knack injuries, and you play through it and suck it up and get it done."

The prize was worth it. But was it his best ever? Woods thought for a moment and replied: "Yeah, I think so. It's either this one or my first one [his 1997 Masters victory].

This week had a lot of doubt to it, to be honest. Now it's just an unbelievable feeling." The winner's cheque worth £675,000 takes his on-course career earnings beyond £50million. But Woods was made to work for his money by Mediate, the 45-year-old who was ranked 157 in the world at the start of the US Open and only got into the lineup by way of a play-off in a qualifying tournament.

Mediate, whose dream of a maiden major title died when he bogeyed the first extra hole, remained typically upbeat.

One of the most popular characters on the US Tour, he said: "I'm sure I scared Tiger. I've never had more fun, it's just amazing. But he's hard to beat. I threw everything I had, the kitchen sink, everything right at him.

"I was three down through 10 and it could have been over pretty quick. All of a sudden - bang, bang, bang - I pick up three, four shots and in a few holes and I'm one up."

Woods squared the play-off on levelpar 71 with a birdie at the last. Then, in the first sudden-death hole at the seventh, Mediate hit his tee shot left into the fairway bunker and the duel was effectively over.

Lee Westwood's third place moves him from 20th to 17th in the world rankings. Sergio Garcia is Europe's top player in sixth place, one ahead of Justin Rose.

As for Woods, this is now his 500th week as No1. Whether he plays again this season or not, he is likely to remain on top for some time to come.