What is the rationale behind PennHIP?
Through a sophisticated biomechanical study, it was found that the hip is loosest when positioned in a neutral or “standing” orientation (also called the stance-phase of weight bearing). It was reasoned that this point is also the optimal patient position for measuring maximal hip joint laxity on a radiograph. Ironically, the standard hip-extended method was found to put the hip in one of its tightest configurations. Next, passive hip laxity was radiographically monitored in dogs as they matured. It was shown that 1) the radiographic measurement of passive hip joint laxity by the PennHIP method was accurate in dogs as young as sixteen weeks of age, and 2) hip laxity was the primary risk-factor to predict the development of DJD. Specifically, the looser the hip joint according to the PennHIP method, the greater the chance that it will develop DJD. The PennHIP method also incorporates the hip-extended radiograph to evaluate for evidence of DJD.
