University of Wisconsin researchers found certain forelimb characteristics in growing Thoroughbreds are associated with higher birth weights, and their carpal (knee) conformation is associated with the parents’. Both genetics and environment affect forelimb conformation.

Scott Leibsle, DVM, of Sawtooth Equine Service in Bellevue, Idaho, said veterinarians recorded the foals’ conformation and body weight every 30-60 days until the foals were 18 months old. They noted if knees were straight, valgus (knock-kneed), offset, or turned out. Fetlocks were graded as straight, inwardly rotated, or outwardly rotated. The authors also graded the parents’ conformation whenever possible.

Heavy birth weights were associated with offset knees and inward fetlock deviation, which suggests that early heavy loads might impact conformation. Similar sire carpal conformation was associated with yearling outward carpal rotation and offset knees, and dam carpal valgus had a very strong trend of association with yearling valgus. There were no fetlock associations between parents and progeny, suggesting there are additional environmental factors associated with fetlock development.

This could help predict how a foal’s conformation will change as it matures, allow for earlier surgical intervention if necessary, and avoid surgery if the foal corrects spontaneously