Bone Chips and Racing Potential in Horses

Bone chips are a fairly common finding on radiographs of yearling Thoroughbreds aimed for racing careers. In a study of radiographs from 5,000 yearlings offered for sale between 2004 and 2007, a team of researchers chose 45 yearlings with bone chips in the back of one or both knees. The chips were on the articular surfaces of the accessory carpal bones. Horses with chips in the right knee numbered 23; 19 horses had chips in the left knee; and three had chips in both knees.

The researchers then looked at racing records for those horses as well as a half-sibling for each horse (foal out of the same dam) that did not have chips on yearling radiographs. Number of race starts, earnings per start, and career earnings were compared. While the number of race starts was the same for horses with and without bone chips, the earnings per start were lower for those horses with chips.

During the two-year-old and three-year-old racing seasons, horses with chips earned about $1,500 less per start than control horses, and therefore earned lower totals in their racing careers.

The researchers pointed out that there are many factors in the success of a particular racehorse, and results from a study with a small sample size might not apply to all horses in every situation.