OFA vs PennHip - The German Shepherd Hip

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Last updated 4/22/13

What is better: OFA or PennHip ?


I often get asked "what's the real 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 a Peach.
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.
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 stay in the socket.


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 ligament, tendons, and cartilage that forms the joint capsule and surrounding tissue that holds the hips socket together
  • Life - Represented by the tailgate of the truck on a bumpy road.
  • 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 actually 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 Sequoyah Shepherds 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 that 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.
I, personally, am going to tell you that I feel that 70-80% of all German shepherds have hip dysplasia. What does this mean?  What exactly is hip dysplasia?  As a veterinarian, I have submitted numerous radiographs to OFA.  Some of them have come back "dysplastic" with no arthritis and some have come back as "passing".  I have resubmitted radiographs on dogs that were judged as "dysplastic" at 2 years of age and THOSE EXACT SAME DOGS came back as "fair" at 6 or 8 or 10 years of age.  I have also resubmitted rads on dogs that were "GOOD" at 2 year of age that "became" dysplastic years later.  The fact is that "arthritis" = "hip dysplasia".  Hips aren't technically dysplastic until you are see arthritis present even though OFA might grade them as "dysplastic" at present WITHOUT arthritis.  OFA scores come from a panel of 3 experts who, based on their opinions, judge the likelihood that the dog in question will become "dysplastic" or "form arthritis" at some point.  

I have stated that 70-80% of all German Shepherds have hip dysplasia.  Most everyone that hears that statement is appalled - either by the statics or with my opinion, as most breeders (and even OFA) says that only 18% or so have hip dysplasia.  If I told you that I had a 11-year-old German shepherd who was starting to get some arthritis in his hips, would any of you think that was abnormal? I dare say that most of you would not. How is that any different from arthritis that develops at three or four years of age then?  It looks the same on a X-ray. It feels the same to the dog. Why is it then that we call it "arthritis" at 10 years of age and "hip dysplasia" at 3 years of age?  Why did one dog get it at three years of age and another dog get it at 11 years of age? Why do some dogs never get it at all, no matter what kind of sports, agility, or other strenuous activities they have engaged in throughout the years? 

Well, let's take a moment to look at people.  I am also going to tell you that 70-80% of all people have knee problems = arthritis (at some point in their life).  Many older people (just like dogs) have arthritis to some extent but not enough to affect them in any significant way.  As, we are fond of saying in the veterinary world, "dogs (humans) walk on their hips (knees), not their xrays".  Many dogs/people have arthritis and show absolutely NO sign of it whatsoever.  Owners love to come in and say things like "my last dog lived to 12 years old and he NEVER had any arthritis".  "Did you xray him?"  "No".  "How do you know then?"  ???  

So what determines "how", "when", or "if" your dog will get arthritis (or "hip dysplasia")?  The answers to these questions are not simple but instead are wrapped tightly within the bounds of genetics, environment, and other factors affecting the development of these dogs through the years.
Many breeders will tell you that environment plays a 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 play 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 actually 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 bodyweight.
So, yes, 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.
So what does all this mean? It means, if you were lucky enough to get a dog out of the top 20% orthopedically in the German Shepherd breed, you have struck gold, my friend. You don't have to worry about whether your dog jumps in and out of the back of your truck, you can go out and play Frisbee with your dog at an early age, you can start agility whenever you want, you can lead a perfectly normal life without having to worry about the developmental stages of your dogs hips. How do you know if your puppy is one of those dogs? The plain and simple answer is ......you don't. Or, at least you don't into your dog turns 12 years of age or so. No amount of research, testing, X-rays, or pedigree studies will be able to truly answer this question for you at this point in time. No breeder guarantee will assure it for you. You can simply do your due diligence and hope for the best. That is what most of the breeders who are offering the longer-term hip guarantees are doing as well. Most of us know what type of dog our dogs are. Most of us know what type puppies they generally produce. Most of us know what type dogs are in the pedigrees. Does this mean that we can absolutely 100% guarantee that your puppy will be hip dysplasia free? Absolutely not. But most of us feel pretty confident that we are doing everything possible to ensure the best genetics that we can and are willing to take that financial risk for you because we are striving to be able to produce that "perfect" puppy.
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 the 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).  That is why here at Sequoyah Shepherds every one of our pups will be placed on limited registration and that registration WILL NOT BE LIFTED until both the hips and elbows are xrayed to prove that the dog is acceptable orthopedically. (There are other restrictions as well but we will focus on orthopedics here.  This requirement also helps us to know what our breeding dogs are producing so that we can improve our breeding program.

So, back to 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, needs 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 improvement their breeding program and the perpetuation of excellence in the GSD 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. 

I know this was a bit of a ramble, but hopefully it has helped clear up some of the misconceptions with the German Shepherd, their hips, and their hip scores. Feel free to give me a call or email me if you have any questions or input.  As I have time, I may also add comparisons to this page of some of the other scoring systems that are used in Canada and abroad.  Thanks! 



Genetics vs Environment Equals......

Genetics: OFA: PennHip: Environment: Results:
Loose ligament and shallow cup Poor Poor Poor Arthritis Early
Loose ligament and shallow cup Poor Poor Good Arthritis Later - but still gets it
Loose ligament and Deep Cup Good Poor Poor Arthritis MOST LIKELY early
Loose ligament and Deep Cup Good Poor Good Arthritis MOST LIKELY later
Short ligament and Shallow Cup Poor Good Poor Arthritis POSSIBLE depending on how tight the PennHip scores were
Short ligament  and Shallow Cup Poor Good Good Arthritis Less Likely
Short ligament  and Deep Cup Good Good Poor NORMAL HIPS - NO ARTHRITIS
Short ligament  and Deep Cup Good Good Good NORMAL HIPS - NO ARTHRITIS


Questions and Answers:  True or False

Let's see what you know.....  :-)

If your dog passes an OFA with a score of EXCELLENT, he will never get arthritis?

If your dog has good hips, it should not matter if he/she is sedated to shoot hip xrays because it will allow for better positioning of the hips on the film and give you a more ACCURATE result. True
OFA prefers that a dog NOT be xrayed within 6 weeks before, after, or during a heat cycle True
PennHip does not care whether a dog is in heat when he/she is xrayed and says that it will not affect the resulting scores True
PennHip xrays cost more because more films must be shot than with OFA True
If you shoot a set of PennHip radiographs, PennHip does not require that they be sent in if you can tell that the hips are going to come back poor anyway. FALSE
If you shoot a set of OFA radiographs, OFA does not required that they be sent in if you can tell that the hips are going to come back poor or dysplastic anyway. True
Positioning of a dog for an OFA film can alter the OFA results from Good to Fair or Fair to Dysplastic but are unlikely to alter the results from Excellent to Dysplastic True
If your dog comes back with a Dysplastic score in one hip and a Fair in the other, it is okay to breed as long as you breed to a mate with very good hip scores False
The older the dog is at the time of the hip certification, the more accurate the results True
If a dog is xrayed at 2 years of age, he will never need to be hip xrayed again because the results will never change. False


Cornell University also has an interesting article on Hip Dysplasia.......