Canine hip dysplasia is a very common orthopedic condition and every small- or mixed-animal practitioner will see cases. Despite this, the management of this syndrome can be frustrating and confusing to the clinician as well as the client. Questions about prognosis, what surgery to recommend (and when), various aspects of medical management and more are difficult to answer definitively. This session and the next one will address these topics from the standpoint of the general practitioner working in a challenging economic climate. This first session will review the diagnosis of the disease and the meaning of the various findings. Additionally, we will explore the fundamental question of whether to pursue medical or surgical management for a given case scenario.

Pathophysiology of hip dysplasia

Whenever the management of a disease process is not straightforward or well-defined, it is helpful to return to our understanding of the pathophysiology in order to guide our course of action. Clinical hip dysplasia arises from a complex interaction of genetic, nutritional and environmental factors. In a simple way, lax hips, perhaps in combination with inherent conformational inadequacies, allow biomechanical stresses to be placed on the adjacent soft tissues and on the joint itself. The stress on the capsule, muscles, and subchondral bone cause pain in young animals even before the development of arthritis. Eventually, the abnormal forces exerted across the joint will trigger the onset of arthritis which will progress to a greater or lesser degree and cause morbidity – even as the previous causes of discomfort fade. Understanding the sources of the clinical signs will help clinicians choose reasonable treatment courses, even though there is rarely a single appropriate course of action.

As with any clinical problem, careful attention to signalment, history and physical examination findings is invaluable even before further radiographs are obtained. For example, pursuing aggressive treatment of a radiographically-diagnosed dog that is actually asymptomatic would likely be inappropriate. Similarly, despite significant disease, some breeds such as English bulldogs rarely require much in the way of intervention – at the least, attention should be paid to searching for other problems such as cruciate ligament tears. Clinical presentations that do not fit the "typical" pattern should be considered as an opportunity to pause and reassess – for instance, young dogs may display marked asymmetry in the lameness associated with hip dysplasia but it would be more likely for such a presentation to be due to panosteitis. Alternatively, an older dog with significant arthritis that suddenly displays lameness may have exacerbated the dysplasia, but is more likely to have sustained a cruciate injury or be suffering from acute spinal disease. Lastly, the physical examination may not provide a definitive diagnosis, but should be consistent with expectations. Findings such as proprioceptive deficits should stimulate a search for other diseases.

Assuming that the initial assessment is consistent with hip dysplasia, radiographs should be obtained. In most cases, standard ventral-dorsal radiographs with the hips extended provide sufficient information. At other times, views such as the PennHIP style or tangential views may be indicated. Radiographs should never be interpreted without also considering the clinical picture.