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The discovery of
carpal osteochondral fragments (COF), commonly known as “knee chips,” on
pre-sale radiographs has long been viewed as a red flag in the Thoroughbred
industry. Horses showing these lesions are often discounted at auction because
buyers assume they will be less likely to succeed on the racetrack. However,
new research suggests that this long-held belief may not be as straightforward
as previously thought.
A study published in the Equine Veterinary Journal by researchers at the University of Kentucky's Maxwell H. Gluck Equine Research Center is the first to directly compare sales and racing outcomes of Thoroughbred yearlings with COF against a matched population of radiographically clean horses. The findings indicate that while the presence of COF can negatively affect both sales and racing performance, arthroscopic surgery may help mitigate some of those disadvantages.
“The idea came from seeing a large number of these cases get significantly marked down in price, just because people assume a chip means the horse won’t perform,” said Bruno Menarim, one of the study’s senior authors. “That was possibly true in the ’80s and part of the ’90s, but not with current arthroscopic surgery approaches.”
Researchers reviewed clinical records from Hagyard Equine Medical Institute between 2015 and 2018 and identified 46 Thoroughbred yearlings with dorsal osteochondral fragments of the radial or intermediate carpal bones. Twenty-six horses underwent arthroscopic removal of the fragments before sale, while 20 were managed conservatively. A control group of 138 sire- and year-matched siblings without radiographic abnormalities was also assembled.
The team then tracked sales and racing records up to June 2023, examining variables including sale price, career earnings, average earnings per start, number of starts, seasons raced, highest speed figure achieved and the highest class of race reached.
Overall, the presence of COF was associated with lower sale prices and reduced lifetime earnings, regardless of treatment. Horses in both the surgical and non-surgical groups also recorded fewer starts and raced for fewer seasons than their unaffected counterparts.
However, important differences emerged when treatment was considered. Horses whose fragments were removed arthroscopically were significantly more likely to achieve a racing career than those managed conservatively. Statistical analysis showed surgically treated horses had more than six times the odds of making it to the racetrack compared with untreated horses.
Perhaps more importantly from a commercial perspective, surgically treated horses were not significantly different from the control group in either sale price or total earnings. In contrast, untreated horses were heavily penalised at auction and earned significantly less during their racing careers.
“In other words, the gap between a surgically treated horse and a clean horse was not statistically significant,” Menarim explained. “The gap between an untreated horse and a clean horse was.”
The researchers also noted that the average difference in sale price between treated and untreated horses was nearly $2,000 - roughly equivalent to the cost of the surgery itself.
The study’s authors caution that the relatively small sample size and single-centre design limit the broader applicability of the findings. Nevertheless, the results suggest that while a history of COF can affect buyer perception, arthroscopic removal may preserve both sales appeal and future athletic potential.
For consignors and owners faced with a yearling diagnosed with a knee chip, the research offers reassurance that the lesion itself need not be career-defining - particularly when modern surgical treatment is employed.
For more details, see:
Daria C Debald, Victoria L Stanton, Cole B Sandow, Dwayne H Rodgerson, Michael A Spirito, Robert J Hunt, Bruno C Menarim.
Racing and sales performance in Thoroughbred yearlings after carpal osteochondral fragment removal.
Equine Vet J. 2026;58(3):682–691
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