[Definition of hip dysplasia in 2023 : Signs of macro and micro instability].

Background: Hip dysplasia is a complex static-dynamic pathology leading to chronic joint instability and osteoarthritis. Because our understanding of the underlying pathomorphologies of hip dysplasia, both on the macro and micro levels, has evolved, an updated definition is needed.

Question: What is the definition of hip dysplasia in 2023?

Methods: By summarizing and reviewing relevant literature, we provide an up-to-date definition of hip dysplasia with a guide to appropriately making the diagnosis.

Results: In addition to the pathognomonic parameters, supportive and descriptive indicators, as well as secondary changes are used to fully characterize instability inherent in hip dysplasia. The primary diagnostic tool is always the plain anteroposterior pelvis radiograph, which can be supplemented by additional investigations (MRI of the hip with intraarticular contrast agent; CT) if necessary.

Conclusion: The complexity, subtlety, and diversity of the pathomorphology of residual hip dysplasia requires careful, multilevel diagnosis and treatment planning in specialized centers.