Study Identifies Causes of Joint Trauma in Young Horses

The joint abnormalities grouped under the term osteochondrosis can be caused by one or more factors including genetic predisposition, unbalanced nutrition, mechanical forces, and an uneven growth pattern in young horses. Osteochondrosis involves various defects in the way joint cartilage matures. Cartilage cysts, shreds, and flaps can cause serious lameness and greatly reduce the value of a sale weanling or yearling. Though some cases self-correct with time, others require surgical intervention, and some are severe enough to prevent affected horses from being able to enter race training or have successful performance careers.

At the Alfort National Veterinary School in Normandy, France, researchers studied a group of 259 horses beginning when the horses were six months old and continuing for 11 months. The horses were chosen from 20 breeding farms in the region. Details of management and environment were recorded, and selected joints were radiographed at the beginning and end of the study to evaluate joint health.

Various defects including fragmentation of joint cartilage, fractures of the growth plate, and defective ossification were identified in 48% of the horses at the beginning of the study, and 42% showed problems at 17 months. More than half the horses had changes in the severity scores during the study, with some horses improving and others increasing in severity. The researchers listed being turned out on rough ground as a risk factor for joint injury. Being kept in mixed housing, where herdmates varied and social altercations were frequent, was also seen as a management strategy that was associated with joint trauma.

Stall confinement or solo turnout in small, level paddocks might seem like helpful management measures to avoid joint injuries in young horses, but stalling has been shown to disrupt the course of bone development, as has a lack of exercise in large turnout areas. Young horses like to run and play with their herdmates, and these activities are important for bone maturation and social interaction. Keeping weanling and yearling herds stable rather than frequently changing a young horse’s pasturemates might be a helpful strategy to prevent more submissive horses from being forced to overexercise while being chased and bullied.