What does the "distraction index" measure in PennHIP evaluations?

The "distraction index" in PennHIP evaluations specifically measures the distance the femoral head (the ball of the hip joint) can be displaced from the acetabulum (the socket) when a force is applied. This measurement is critical in assessing the stability of the hip joint and the likelihood of hip dysplasia in dogs. A higher distraction index indicates a greater ability for the femoral head to be pushed out of the socket, which signifies a less stable joint. This evaluation is essential for breeders and veterinarians in determining the risk of hip dysplasia and making informed decisions about animal health and breeding practices. The other options relate to different aspects of health and fitness, but none pertain directly to the specific assessment of hip joint stability that the distraction index provides.