Dropped Pasterns
Perhaps a little story will help illustrate this month's question and health problem.
I have a good friend in the Working Dog industry. This person starts a new dog every five years or so, so her time investment is considerable. She was looking at a two-year-old male import. The dog was impressive with solid muscle development and a really nice presence and awareness. We took him out to the field to watch some movement. He looked pretty good but I noticed on a trot his front pasterns nearly touched the turf. He was not lame but I was concerned at this age why he was overextending on the pastern or carpal joint.
I suggested several things at that point. First, we needed to know the dog's history. Has he been kenneled all of his life on concrete in small runs? What has his diet been? Has he been given calcium supplements? What was his workout schedule? Most importantly, what are his parents and grandparents like? I wanted to see pictures of them at a young age and at various life stages if possible.
So what causes dropped pasterns? First, a little definition is in order. Dropped pasterns is simply the over-extension of the carpus and maybe other joints of the paw. The over-extension is basically where the tendons on the underside of the carpus stretch out so far that the joint bends farther than it should (hyperextension) sometimes all the way to the ground. Often the condition leads to severe arthritis and lameness, especially later in life. As with most dogs I our world, as I have said in the past, there are no simple answers and most problems are multi-factorial. Over-extension of the carpus is fairly common, especially in the German Shepherd Dog and Rottys. Whenever there is a problem that is over-represented in one or two breeds usually it means that there is a large genetic component to the problem and, of course, dropped pasterns is no exception. If a dog is genetically predisposed in the first place then some of the other considerations may make the problem more pronounced.
It has been proposed that raising pups and dogs on concrete will cause the condition. I think that perhaps concrete runs will make an existing condition worse but probably will not be the sole cause of the problem. My reasoning is that there are a lot of dogs raised in concrete runs and most do not develop dropped pasterns. Having said this, however, I do prefer pliable flooring whenever possible. Smooth pea gravel, or grass or rubberized flooring is not only easier on the pastern joints but is also easier on the whole body. Any of you runners out there know the difference.
Injury can most definitely be a cause of dropped pasterns and the most common type of injury occurs from over work. As the dog is exercising all of the tendons and muscles will stretch and contract. If the work goes to exhaustion levels some of the mechanisms to prevent over-extension are not functioning as well. This injury is very common in the horse and not as common in the dog but it does happen. Once over-extension occurs permanent damage may result in the form of avulsed tendons (tearing of the tendons where they attach to bone), small bone fractures and more. Rest and rarely surgery are the possible fixes to these injuries.
Another type of injury is the simple misstep (or stepping into a hole) resulting in over extension that can give the same results as above. Usually I find that this injury affects just one leg more often.
Finally, nutrition can play a huge role in dropped tendons. The problem was pretty common when calcium supplementation was common practice. Probably the mechanisms of the problem here was that the Phosphorus/Calcium balance was off resulting in irregular and unmatched tendon and bone growth which then sets off the downward spiral of abnormal development.
I should also mention that dropped pasterns in a growing animal could be perfectly normal. I have seen some pretty severe cases become normal just by growing up.
The gist of all this discussion is that dropped pasterns, which is a fairly serious condition in the Working Dog can be a complicated mix of several factors. By judicious research of family genetics, applying basic nutritional principals and following a sound training program one will greatly decrease the chances of dealing with this potentially debilitating condition.
Gary Cotton, D.V.M.