It should have been the best day of Jennie Harrington's life. Joining English National Ballet and dancing in the chorus of Cinderella was the fulfilment of a lifetime ambition - but the pain gave her the shock of her life. "I came off stage, walked into the dressing room, and burst into tears. The other girls said, 'Oh my God, what's wrong?' When I told them, they said, 'Is that all?'"

Years of ballet school hadn't prepared Harrington, now 23, for the agony of the professional circuit. Begoña Cao, a soloist with the ENB and three years her senior, remembers telling Harrington she would get used to it. She had some other advice, too: "Keep smiling - it lifts you up. Otherwise you cry."

Go to any ballet house and, however serene the dancers' faces, those elegant pink silk shoes hide a battery of injuries: black nails, purpling flesh, growths galore. Peter Norman, one of the UK's leading podiatrists, has seen it all in the 16 years he has been treating the the Royal Ballet. He is aware, too, that even more goes on unseen. "I know of dancers who have gone on pointe with broken bones and stress fractures," says Norman. "The pressure on them to get parts, to guard their places in the companies, means they push themselves too far."

Most dance companies now employ physiotherapists, even masseurs, on staff, but dancers' feet remain areas of private hell. "I've never seen a podiatrist," admits Cao, who is 26. "I'm too scared. And too embarrassed - I know I've got the worst feet." While the US has a large network of foot specialists for dancers, in the UK Norman is the only one of his kind.

When Harrington began her career, she found a chiropodist in the Yellow Pages who had no previous experience with dancers, and now sees her once a year. "She tells me she has 80-year-old patients who have better feet," Harrington says. They have found ways to manage her pain; Harrington begs the chiropodist not to remove the thick layers of dead skin, since they're the only thing preventing her from getting too many blisters. For most dancers, blisters, bunions and corns are the norm, the inevitable result of feet compressed into unforgiving pointe shoes (with blocks built up using layer upon layer of hessian triangles, paper and glue) that give the illusion of dancing on tiptoe.

With constant wear, the kind of minor ailments that most people would find merely irritating become self-perpetuating agonies. Corns develop sinuses and become ulcers; nails thicken and grow hard skin underneath; and dancers, compensating for one kind of pain, risk putting undue stress elsewhere, causing new injuries. While podiatrists such as Norman can provide palliative care and treat infections with antibiotics, even his work has its limits. "I see many problems that require a week or a month's rest," he says. "But 'take a night off' is as much as I can say, or they wouldn't come back to me again."

Michael Nunn, first soloist with the Royal Ballet company before he and William Trevitt formed their own company, the Ballet Boyz, says dancers often refuse to admit they are in trouble. "When you're part of a big company, you're always wanting to elevate yourself within the hierarchy. You don't want to be seen as the one who's injured. So people do push themselves more, especially when they're young." He has done it himself, dancing with a damaged achilles tendon for 18 months before finally going for surgery. By that point, it wasn't easy to find someone willing to take on the job.

Men, who wear softer canvas shoes, suffer different problems from women. Jumping and lifting put the biggest strain on their feet, so ankle and muscular injuries are common. Trevitt remembers playing Oberon in A Midsummer Night's Dream with a twisted ankle. "I couldn't move it sideways or flex it because it was too painful, so I didn't do the part too well. But it was a big role and I really wanted it." He and Nunn have been far more careful since they started out on their own, because if they don't perform, the company doesn't get paid. "At the bigger companies, you don't get to choose whether you've done enough on a particular day," says Trevitt. "You just have to keep working."

Most dancers have also had at least one bad experience with a doctor who has made them wary of seeking medical advice: the most common is being told by a GP to give up dancing. Norman's very first dance case, 20 years ago, was that of a prima ballerina whose career was nearly ended by a doctor's insensitive treatment of ulcers between her toes. "Reassuring dancers can be tough," he says.

There is the added complication of the language barrier: Norman administers to dancers from around the world. "You have to explain very carefully what you're going to do. If you're removing a nail, they're terrified they'll never be able to dance again - but in fact some can dance the same day."

In the meantime, self-treatment is the norm. Some is benign: wrapping feet in tape, or lamb's wool, or stuffing chamois leather and old pairs of tights into pointe shoes. Some dancers have more eccentric rituals, such as blowing into shoes before putting them on, or covering their feet in glue and other chemicals to make them stick. More dangerously still, many attack their feet with scissors and razor blades.

The question of pain management raises a laugh from almost every dancer I speak to. "There's something called ... Nurofen," says one. Another jokes that it's a sponsorship opportunity missed. The culture of popping painkillers is widespread. "You don't stay on one brand for too long," explains Nunn, who has stopped taking them since setting up the Ballet Boyz. "As long as you change fairly often, they keep working."

Ask which is the most painful ballet to dance and the women are unanimous: Swan Lake. With its endless pas de bourrés - running tiptoe on the spot - and the chorus appearing in all four acts, there is no let-up. "Doing it in the round at the Royal Albert Hall is a killer," says Harrington, "because it's such a huge stage to run around." The intensity of the steps means that as soon as you stop, cramp floods your legs and feet. Try that eight times a week and your feet swell so much you have to ice them just to be sure of getting them back into your shoes. Dance of the Cygnets? More like Murder on the Dancefloor.

Jennie Harrington

English National Ballet

"I've had a broken toenail but it's getting better now. It's awful, really painful. I was wearing shoes that were too soft so my nail cracked, but I didn't even realise until I got home and saw the blood in my shoe. You're so used to bruised toenails, you just get on with it. It's quite masochistic"

Kei Akahoshi

ENB

"I had to take a night off from Sleeping Beauty last season because of a bunion on my left foot. It got really bruised. The side of my foot went totally black and my big toe was all numb. I wear a support bandage and some pads over my toes, and use furniture polish to harden up my shoes"

Hannah Bateman

Northern Ballet Theatre

"I'm lucky because my feet are square, so all my toes are the same size. People have problems when their second toe is bigger than the first: the pressure doesn't distribute equally. Your first injury is always the worst, because it scares you. I have a recurring neuroma [inflammation] on one of my toe joints. I control that with ice and strengthening exercises"

Michael Nunn

The Ballet Boyz

"I broke my left big toe playing Benvolio at the Royal Opera House. The floor cloth was full of holes, and I got my toe stuck in one. That didn't heal for 18 months. When they opened it up they found some bone fragments that were aggravating it. The four-inch scar on my left leg is from an operation on my achilles tendon. I've broken one of my right toes, too"

Begoña Cao

ENB

"I broke a metatarsal on stage once. I was performing a solo and heard this crack. I didn't realise I'd broken it at the time, because you're used to taking pain. I also get soft corns - little bits of hard skin between your toes. They're agony when you're on stage"

Kenneth Tindall

Northern Ballet Theatre

"I sprained my ankle recently, after landing badly from a jump. I performed the next week - it was really painful and still quite swollen. I've seen dancers go on stage strapped up when they really shouldn't be on at all. That's just a dancer's life"

William Trevitt

The Ballet Boyz

"We dance barefoot so we get a lot of unpleasant hard skin that splits at the joints of your toes. I've got one big toe an inch shorter than the other one, so I have to wear different size shoes. I was diagnosed with club feet when I was born, and my mother was told that if she wanted me to be a dancer she could put my shoes on the wrong feet to correct them - but she didn't"

· English National Ballet's Alice in Wonderland is at Manchester Palace Theatre (0870 160 2832), October 19-28, then touring. Northern Ballet's The Three Musketeers is at the Alhambra, Bradford (01274 432 000), September 23-30, then touring. The Ballet Boyz perform Encore at Sadler's Wells, London EC1 (0870 737 7737), September 26-October 30