In today's domestic dog population, both purebred and mixed-breed dogs are influenced by selective breeding decisions. In large breeds, selection often focuses on body weight, bone strength and power, which can create a mismatch between skeletal load and the resilience of soft tissues. This can favour orthopaedic conditions such as hip and elbow dysplasia or cruciate ligament rupture.
In small and short-nosed toy breeds, an extremely compact body shape is often bred for aesthetic reasons. This can lead to structural problems such as patellar luxation, intervertebral disc disease or brachycephalic syndrome. Overall, breeding criteria can reinforce genetic and structural weaknesses that would be less likely to persist under natural selection.
