It is a pathology that consists of an abnormal formation of the hip joint, with insufficient and irregular fitting of the femur's head in the acetabulum and/or joint and bone degeneration (osteoarthritis). Although there are environmental factors, such as poor diet, slippery floors, excessive physical exercise, which may increase the onset and development of the problem, hip dysplasia has a genetic and hereditary component, without which it is unlikely to occur except in exceptional cases ( accidents and severe trauma). ​ It is common in large and giant breeds, although several other medium-sized breeds report considerable numbers of cases. Although the prevalence is lower than that of several popular breeds in which there are no specimens with normal hips, this pathology is also found in the Estrela Mountain Dog. Prof. Mário Ginja's PhD research, carried out between 2003 and 2008, about HD in this breed, concluded that the average incidence in the Estrela was grade C (mild dysplasia), although there were also cases of moderate and severe dysplasia, as well as others with normal hips or almost normal (the classification used in Portugal is from A to E, representing: A = normal hips; B = almost normal/borderline hips; C = mild dysplasia; D = moderate dysplasia; E = severe dysplasia) ​ Conscientious breeding practices, with rigorous and systematic control of the problem, tend to have good results, in the same way that adequate care for the puppy's growth can prevent the development of dysplasia or, at least, the emergence of symptoms.