What is PennHIP?
PennHIP stands for the University of Pennsylvania's Hip Improvement Program.
PennHIP is a state of the art, multifaceted radiographic technique for hip evaluation. The technique assesses the quality of the canine hip and quantitatively measures passive hip joint laxity. The PennHIP evaluation method is more accurate than the current standard in its ability to predict the development of osteoarthritis. Osteoarthritis, also known as degenerative joint disease (DJD), is the hallmark of canine hip dysplasia (CHD).
Above: Pictures of PennHIP's distraction view.
PennHIP is more than just a radiographic technique. It involves a network of veterinarians trained to perform the PennHIP procedure properly and it has a large scientific database that houses all PennHIP data. The radiographs are sent in from certified PennHIP members worldwide to the PennHIP Analysis Center for evaluation. The resulting data is stored in the database, which is continually monitored as it expands. As more information becomes available, the PennHIP laboratory is able to obtain more precise answers to questions about etiology, predictability, and the genetic basis of CHD.

The PennHIP laboratory publishes its findings in scientific journals. Published information is disseminated to all PennHIP members; it is also shared with interested breed clubs and routinely appears in publications within the dog fancy.

PennHIP is composed of three major components:

  • A diagnostic radiographic technique
  • A network of trained veterinarians
  • A medical database for scientific analysis
Introduction to the PennHIP Method
The PennHIP method is a novel way to assess, measure and interpret hip joint laxity. It consists of three separate radiographs: the distraction view, the compression view and the hip-extended view. The distraction view and compression view, developed by Dr. Smith, are used to obtain accurate and precise measurements of joint laxity and congruity. The hip-extended view is used to obtain supplementary information regarding the existence of degenerative joint disease (DJD) of the hip joint. (The hip-extended view is the conventional radiographic view used to evaluate the integrity of the canine hip joint.) The PennHIP technique is more accurate than the current standard, and it has been shown to be a better predictor for the onset of DJD.
The radiographs pictured here are of the same dog, yet the hip joint laxties in each view look very different. Notice that the hips in the distraction view appear to be much looser than they do in the hip-extended view.

The obvious contrast in joint laxity between the distraction and hip-extended views demonstrates the fundamental difference between the two radiographs. The looser the joint on the distraction view, the greater is the chance that the hip will develop DJD. The hip-extended view tends to mask true hip joint laxity because the joint capsule is wound up into a tightened orientation when the hips are extended. This explains why measurable joint laxity on the distraction view is always greater than the measurable laxity from the hip-extended view. In fact, distraction laxity is up to 11 times greater depending on the breed of dog under study.

The compression view is used to determine the "goodness of fit" of the femoral heads into the acetabula. In a hip with DJD, the remodeling that occurs in the acetabulum and/or the femoral head will often result in an ill-fitting "ball" and "socket".

To summarize, the PennHIP method:

  • Obtains DJD readings from the standard hip-extended view
  • Obtains hip joint congruity readings from the compression view
  • Obtains quantitative measurements of hip joint laxity from the distraction view
Advantages of the PennHIP Method
Hip screening can be performed as early as 16 weeks of age.
The method utilizes quantitative measurements as opposed to subjective scoring.
The positioning used allows assessment of true passive laxity.
There is repeatability of the distraction procedure within and between examiners.
The method provides risk assessment of hip dysplasia development.
PennHIP compares laxity measurements with others of the same breed.  This information is useful for making informed breeding decisions.
The PennHIP method has the lowest false negative and false positive diagnosses of any current screening method.
The PennHIP method has the highest heritability of any screening method.