OFA vs PennHip and why does Sur le Delavan Kennel test both ways?

What is better: OFA or PennHip?

I often get asked, “what’s the difference between OFA and PennHip”. I am going to attempt to answer that question here without getting into the extreme technical issues involved as well.

It would most likely take me hours to really go over the major differences between the two systems, the pros and cons of each, and why they don’t always agree. I will try to simplify it a little here. Everybody tries to compare the two. There really is NO comparison – they may both be fruits, but they are most definitely NOT the same fruit…. just as an Apple does not equal an Orange.

I will agree that both techniques, PennHip and OFA, are means of scoring hips, however, just because you score well with one system does not mean you will score well with the other system. THEY DO NOT MEASURE THE SAME THING. THEY ARE NOT EQUAL.

  Normal - Good Hips   OFA X Rays                               Bad - Dysplastic Hips   OFA X Rays                                                                          


If you get an average score on PennHip, that does NOT necessarily equal a FAIR score on OFA. If you get an EXCELLENT score on PennHip, that does NOT necessarily mean you will even PASS an OFA. Make no mistake, they DO NOT compare.

OFA measures how DEEP the hip fits in the socket. PennHip measures how TIGHT does the hip stays in the socket.

Compression View PennHip                             Distraction View PennHip                     Extended View                                                                                                                        PennHip 

What does this mean?

Here is your glossary:

Acetabulum – the “cup” on the pelvis that the head of the femur fits in forming the hip socket. It can be deep (a cup), shallow (a saucer), or somewhere between.

Femoral head – the ball-shaped top of the thigh bone that fits into the acetabulum.

The “string” – the series of ligaments, tendons, and cartilage that forms the joint capsule and surrounding tissue that holds the hips socket together.

Arthritis – what happens when the ball either moves around too much in the cup/saucer or falls off of it completely.

With OFA, they want to see a deep cup (acetabulum) with the ball (femoral head) down deep inside it. Obviously, this is important – if you are trying to take something with you down the bumpy road of life, it is better to take it in a “cup” than a “saucer”. And the deeper, the better.

On the other hand, PennHip does not really care how deep the hip fits in the socket, it merely evaluates how much movement “in” (Compression) and “out” (Distraction) of the socket there is. In other words – Does it STAY in the socket.

The comparison that I use for this example is similar to the OFA comparison. If you were riding down that same bumpy road of life on the tailgate of the truck, we have already determined that if you wanted to take, say a ball, with you, it would be much better to have that ball sitting in a cup rather than a saucer. But let’s take it one step further. Let’s say that we could anchor that ball into either the cup or the saucer by using a string (ligament).

If that ligament is too long, you increase your risk of the ball falling out of your cup/saucer. So, obviously, we would want a string that is very short and very tight. If the string is very short and very tight then you would get a good score on your PennHip. However, even if the string is very short and very tight, if the ball is sitting inside of a saucer instead of a cup, or if the ball simply does not fit in the cup at all (incongruity in the joint) your OFA’s will be very poor.

Now let’s look at it from the opposite direction. Let’s say that you definitely have a cup that you’re working with. Let’s say that the string (ligament) that holds the ball in the cup is very long. Now, you will most likely have a very good OFA score but a very poor PennHip score.

Or, what if you have a saucer that you’re working with and a very long string? Chances are that you will not go very far down that road of life before your ball falls out of your saucer (aka – your dog starts showing arthritis). You would have most likely had a poor OFA score and a poor PennHip score.

What if you have a saucer and a very short string? The ball most likely will not fall off from the saucer. This will equal good PennHip scores and poor OFA scores.

So, what does it all mean? Here at Sur le Delavan Kennel, we feel that it is important to have both passing OFA scores, as well as good PennHip scores (PennHip doesn’t actually give you a pass or fail, they give you your dogs scores when compared with other dogs of ONLY that same breed – these are given in percentages …. i.e. your dog is better than 70% of the breed, or your dog is in the top 30% of the breed.


The nuts and bolts of it are these...

If you have a deep acetabulum (good OFA scores) where the ball will fit down deep into the hip socket, you are less likely to have wear and tear on the acetabulum itself because the ball obviously is more likely to stay put. However, if you don’t have a good PennHip score, meaning the ball actually stays in the hip socket, it really doesn’t matter how deep it actually will fit in the socket if it won’t stay there. That’s kind of like putting a wheel on an axle – if you don’t anchor it down, it is going to fall off eventually when you go down the road. So, IMO, it does not matter how good your OFA scores are if your dog cannot get a decent PennHip score.

Conversely, even though a dog passes his PennHip, does that mean you can ignore OFA? You should easily be able to tell that if the femoral ball is sitting on a saucer instead of a deep acetabulum, even with a short “string” or ligament, there is more likely to be “play” in the hip socket. Any movement in the joint that indicates laxity increases the risk of arthritis.

Many breeders will tell you that environment plays the biggest role in the development of arthritis. I, personally, do not believe it is true but there is something to be said for this argument.

Now let’s get back to people… If you have a person that played football professionally through most of his adult life and retires at 40 years of age, none of you would be surprised to find that he has arthritis in his knees, even if he has NEVER suffered an actual knee injury. Why? The obvious answer is that he participated in a sport that environmentally dramatically affected his knees through the years. However, explain to me why there are some men who have played football professionally throughout their life and at 40 years of age still have excellent knees. ANSWER: Genetics.

If that same man who played football and developed arthritis had spent most of his life as a white-collar worker sitting behind an executive desk, would he have gotten arthritis? The answer is.… Maybe. It would’ve depended on how “bad” his knees were – how loose were the ligaments? how deep were the sockets? Just as with some dogs, no matter what you do, they are going to develop arthritis at a very early age. Those same dogs, if they are put through strenuous activities at an early age, such as agility, Schutzhund, Frisbee, etc. will generally develop much more severe cases than if they spent most of their life in mild to moderate activity range with a normal to lean body weight.

So, yes, the environment does play a significant role in the development of arthritis. But what about GENETICS?

Now, let’s go back to the guy who played football and did not develop arthritis. The long and short of it is… he had excellent genetics, to begin with. When you have excellent genetics, to begin with, ENVIRONMENT will play LESS of a role than if the genetics are questionable to poor.

By using both OFA and PennHip as means of evaluating the quality of the breeding dog, breeders can better assess the likelihood of those dogs passing on “fair” to “poor” genetics. Does that mean you don’t have anything to worry about? Does that mean you don’t have to use a little common sense? Absolutely not. Though we do our best to ensure that the dogs we are breeding are as close to that top 20% as we can get, none of us are willing to stake our life on the fact that YOUR puppy will never develop arthritis. There are too many factors involved in genetics that we simply do not completely understand at this point that are affecting the quality of the offspring. Two very nice breeding dogs can produce puppies with poor quality hips (or at least hips that are not of breeding quality).

So, back to the environment …. There are things you can do to decrease the risk of developing arthritis in your puppy should he/she GENETICALLY not fall in the top 20-30 percentile. If your puppy does not happen to be in the top percentages, obviously it would not be a good idea to take him out and start doing frisbee work with him during the formative stages of his joints. Obviously, it would not be a good idea to feed a poor-quality food that has a disproportionate calcium/phosphorus ratio or excessive amount of calcium within the food – this, too, will hurt the formative stages of his joints – nor do you want to allow him to gain weight to fast or become excessively heavy.

So, what it boils down to is…. everyone has a role to play. A breeder should do the best they can to ensure that they are dealing with the best genes, and you, as the owner, need to make sure that your puppy is fed properly, maintains the proper weight, does not participate in high impact activities at an early age, and stay in contact with your breeder reporting back on any problems that you may have with your puppy. This feedback will not only help ensure that your breeder is able to assist you in any way they can, but it will also help them to be able to better select the good genes out of the gene pool and therefore improve their breeding program and the perpetuation of excellence in the EB breed itself. With everyone working together, we will help improve the quality of the life of the breed we all love.

And I, for one, feel that one of the best ways that we as breeders can help ensure the best genetic material being passed on to the offspring is by performing both OFA’s AND PennHips and expecting our breeding dogs to pass both scoring systems. Is it fail-safe? No, but it is by far better than any other system out there.

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