After five punishing days, 91 testing holes and nearly 35 miles of walking up hill and down dale, Tiger Woods made the US Open his 14th major title on Monday. But when he stepped up to the make the winning putt against Rocco Mediate, was it a step too far?

That was the question being asked today by rivals and medical experts, many of whom believe Tiger's decision to compete at Torrey Pines against doctor's orders may have jeopardised his dream of beating the record 18 majors claimed by Jack Nicklaus.

As Woods contemplated reconstructive surgery to repair the anterior cruciate ligament in his left knee and treatment for a double stress fracture of his left tibia, the 32-year-old American said: "My doctors assure me with the proper rehabilitation and training, the knee will be strong and there will be no long-term effects."

But Woods will be off the golf course at least until the end of the year and medical opinion is divided about his prospects.

Prominent New York knee surgeon Ronald Grelsamer believes there is more to the story than has been told.

Grelsamer suspects there is damage to the articular cartilage; a smooth, glistening white tissue in the knee that is critical to the joint's movement.

"I would be more concerned about bone and articular cartilage tissue than I would be about ligaments," Grelsamer said, adding that articular cartilage damage can be a greater threat to a sportsman's future than a torn ACL.

" It can require microfracture surgery," he said. "Some athletes come back from microfracture surgery good as new, some are finished."

Dr Rich D'Agostino, a chief orthopaedic surgeon who treats players with the New York Yankees baseball team, said Woods was entering the unknown with an injury affecting a knee which takes so much of the strain from his whipping driving action.

"Who knows what the long-term effect is on his knee?" D'Agostino said. "Who knows how much degeneration has happened already?"

Fellow major winner Vijay Singh revealed the concern in the locker room.The Fijian said: "He needs to fix his knee. The sad thing is it's the wrong knee. It's the left knee that takes all the torque."

Woods's pain will be shared by his rivals, who weekly chase huge prize money and endorsement contracts boosted by the global appeal of the world No1.

Kenny Perry, who played with Woods on the US Ryder Cup team in 2004, conceded that Woods's absence for the rest of the season would be sorely felt.

"It's going to be tough for the sponsors and the Tour," he said. "Tiger is our tour and when you lose your star player, it definitely hurts."

Ty Votaw, executive vice-president for the USPGA Tour, said: "We're not going to sugar-coat the fact that there may be some fall off in TV viewers."