IT'S the subject of whispered conversations over cocktails deep within Flemington's Birdcage. The secret weapon a flock of fashionistas rely upon to teeter upon 10cm stilettos all day long at the races.

Botox and filler injections for the feet are the latest crazes in cosmetic surgery to make their way to Flemington - and the solution, according those with cash to splash, to the old racing conundrum of how to wear those towering pumps and not end up carrying them home after the final race has been run.

For about $1500, some doctors, such as Bondi-based cosmetic surgeon Michael Zacharia, will inject hyaluronic acid (Restylane) into the balls of the feet.

The fluid, commonly injected into joints to treat osteoarthritis, numbs the parts of the foot that become strained by wearing sky-high heels.

And judging by the height of the footwear that was racing out the door of Melbourne boutique Miss Louise yesterday, 10cm heels will indeed be spotted around the Birdcage today.

Dr Zacharia, who has been doing the procedure for just over a year, said the foot filling provided "internal padding for the feel at that point of pressure underneath the balls of the feet. Instead of using those silicon pads inside your shoes, this is an internal way of doing it."

The procedure, however, is a lot more expensive than purchasing a pair of silicon inner-soles. At $750 per foot, the fillers will last for about six months.

Dr Zacharia said three or four people this week had told him they wanted the foot fillers for the Spring Racing Carnival, but he warned those considering the treatment that the sensation immediately following the injections could be uncomfortable.

"I've been told that for about 10 minutes afterwards it feels like you are walking with marbles in your feet, or it's like there is something in your shoe," he said.

The other procedure women are turning to is "bootox" - having Botox injected into the balls, arches and soles of the feet to paralyse the sweat glands, which Dr Zacharia said would also set you back about $1500.

Australasian College of Podiatric Surgeons president Mark Gilheany said while women might think the procedures were magic solutions to stiletto-fatigue, foot fillers could be masking symptoms of more serious problems.

He warned that for people experiencing a significant amount of pain standing in heels it could be a sign of partially dislocated bones or torn ligaments.

"If you require something of that (surgical) nature then you could have an underlying problem," he said.

"It's not something that is routinely done and I haven't seen any clinical trials to say whether the injection of a biological cushion into the foot is effective.

"If there was anything that really worked I'm sure I would know about it. It seems like a waste of time when you can stick a cushion in your shoes and take some paracetamol."