Facing six weeks on the sidelines after damaging a ligaments in his right ankle, Robin van Persie, a striker for Arsenal in the English Premier League, did what any reasonable person in his situation would. He decided to go to Serbia and let a housewife rub horse placenta on the ankle. The procedure supposedly introduces proteins into the injured area, and several soccer players have already tried it. "It can't do any harm, and if it helps, it helps," said Van Persie.

Strange? Yes. Gross? Certainly. But not unprecedented in the annals of unconventional remedies. A few others:

Baby urine. After beating Samuel Peter to regain the WBC heavyweight title in 2008, Vitali Klitschko wrapped his hands in the wet diapers of his three-year-old son, Max. "Baby wee is good because it's pure, doesn't contain toxins and doesn't smell," said Klitschko, whose grandmother gave him the idea. "The nappies hold the liquid, and the swelling stays down."

Emu oil. Shortly before the 2003 London Marathon, Paula Radcliffe collided with a bicyclist and suffered a dislocated jaw, whiplash and cuts and bruises. To hasten the healing, she used an old aboriginal treatment: a balm extracted from the fat of an emu, a speedy, three-toed Australian bird. A month later Radcliffe defended her title in world-record time.

Hornet juice. In 2000 Naoko Takahashi attributed her win in the Olympic marathon in Sydney to an elixir made from the stomach fluid of killer hornets, which purportedly improves endurance. Why hornets? They fly up to 60 miles a day—at nearly 20 mph—in search of food.

Rooster combs. Several athletes have sought treatment from unconventional German doctor Hans-Wilhelm Müller-Wohlfarth, whose medicine of choice for joint problems is an injectable lubricant called Hylart, which is extracted from the bumpy growths on roosters' heads. His most successful patient: cricketer Darren Gough. "I'm the Tin Man," Gough said in 2005. "I go to see him for an oiling every month." Gough's bum knee healed so well that he not only recaptured his form as a bowler but also won the British talent show Strictly Come Dancing.

PHOTOMAX ROSSI/REUTERS (VAN PERSIE)FOAL PLAY Van Persie's horse-placenta treatment is the latest cure from the animal kingdom. PHOTODABJOLA/FOTOLIA (HORNET)[See caption above] PHOTOCHRIS HEPBURN/GETTY IMAGES (ROOSTER)[See caption above] PHOTOERIC ISSELEE/FOTOLIA (EMU)[See caption above]