Hip dysplasia is a condition where the acetabulum is shallow leading to abnormality in the weight bearing zone or concentration of pressure load. Normally, pressure forces in weight bearing are widely distributed over the femoral head.
Acetabular dysplasia reduces the weight-bearing zone in the hip leading to abnormally high pressure in the anterolateral zone of the acetabular margin that may lead to labral hypertrophy and subsequently detachment which can, quite commonly, be radiologically seen as os acetabulare (Figure 7) after labral calcification.
Labral detachment further increases the contact stress between the articulating surfaces and ultimately the actabular cartilage delaminates and progresses to osteoarthritis. The cause of acetabular dysplasia is typically congenital/developmental, although there are conditions during the childhood like Perthes that may lead to secondary dysplasia of the hip.
Femoral deformities, such as coxa vara or anteversion, can similarly cause concentration of the pressure forces over a small area, which is likely to break down.