When thoroughbred horses break a leg, the injury is often life threatening -- a situation put into sharp focus by Kentucky Derby winner Barbaro's struggles after his injury at the Preakness in May.

Barbaro is still in the headlines, and still fighting for life. But since May, 16 lesser-known racehorses have been put to death after injuries at the Arlington Park racetrack near Chicago.

Track officials hired an outside consultant to inspect Arlington's dirt surface. The study failed to turn up any hard evidence that track conditions were causing the horses to falter. But the track decided to add ground pine to the surface to help absorb moisture and make the track softer.

Meanwhile, the state racing board is seeking funds to add a fifth veterinarian to examine horses before each race.

Many possible causes for the injuries are under discussion. Do breeding tactics put too much of an emphasis on speed and too little on stamina and sturdiness? Are medications affecting some horses' performances? And -- in a state with a shortage of thoroughbreds and an increase in racing events -- are horses getting enough rest between races?

Trainer Chris Block, who works with 46 horses at Arlington Park, doesn't expect a definitive answer to why there have been so many breakdowns this year. He and others think the track may simply be struggling through a spate of bad luck.

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