Cycling/Tour de France: As the Lance Armstrong years progressed, and attention focused on the Texan's celebrity, with speculation on whether he had used banned drugs and the question of how many Tours de France he was going to win, the fact he had defied medical logic by merely being at the Tour tended to be overlooked.

Turning medical logic on its head in the Tour is becoming an American tradition. After Armstrong the cancer survivor came Tyler Hamilton, who finished fourth and won a mountain stage in 2003 while riding with a cracked collarbone - although the findings of the Operation Puerto doping scandal in Spain appear to have put that performance in a new light. And yesterday it was revealed that the man who is now in pole position, Floyd Landis, is due to have a hip replacement.

Landis broke the hip-end of his femur at the end of 2002 in a training crash and since then has raced in pain; the fracture is held together by three four-inch titanium pins, and a degenerative condition called avascular necrosis, or osteo necrosis, has set in, which occurs when scar tissue obstructs blood vessels in the hip and the ball joint is damaged.

"If I hadn't had a bicycle racing career I would have had the hip replaced two years ago, because I don't really want to deal with the pain," Landis said in the International Herald Tribune yesterday. "It's bad, it's grinding, it's bone rubbing on bone. When I pedal and walk it comes and goes, but mostly it's an ache like an arthritis pain."

Landis had an operation two years ago to ease the pain, and the surgery left his right leg an inch shorter than his left. He has special dispensation to have cortisone injected into the hip during this Tour to ease the pain. He is expecting to have the operation at the end of the year.

Even so, he will enter the Pyrenees tomorrow as most followers' favourite for the overall title along with the German Andreas Kloden.

His injury and the effect it will have on him in the next 10 days are merely more variables in a race that is more open than it has been seen since 1983. As the field rested in Bordeaux yesterday, there were perhaps a dozen riders who had the potential to win - on paper, at least, or with a little stretch of the imagination - grouped over two and a half minutes.

"Going on past form, Kloden and Landis are the favourites," says Cyrille Guimard, the French team manager who directed Bernard Hinault to his first four Tour wins. "But you could take a decent punt on a guy who is five, six or 10 minutes back."

Landis will go into the Pyrenees as favourite partly because of the way he limited his losses to race leader Serhiy Gontchar on Saturday in the Rennes time- trial, but also because, as the hip episode shows, he is a man who is famously indifferent to pain.

He is also utterly determined, having fought against the constraints of his Mennonite upbringing to race his bike. More interestingly, this year he has shown a new side, winning three important stage races, including the Paris-Nice.

Kloden, on the other hand, has nothing apart from a second place on one stage in last year's race to indicate he has built on his second place overall in 2004.

The Australian Cadel Evans at least has managed to win a major stage race this year, while the least that can be said for Gontchar is that he has shown remarkable consistency in the Giro d'Italia for almost 10 years.

The race will thus pedal south today in almost as uncertain a state as when it started out, with the only certainty being that Landis has shown a little better than the rest, Gontchar is the strongest time-triallist and T-Mobile have strength in depth.

All bets are off, according to Guimard. "As it stands today, an average rider who climbs and time-trials okay and who is less than eight minutes behind could win the Tour. It's a crazy race, sheer anarchy."