Do the Dew(claws)?
The Anatomy of Dewclaws
Miller’s Guide to the Anatomy of the Dog, a veterinary anatomy text, has an excellent figure depicting the muscular anatomy of the distal forelimb. There are 2 functional muscles, the extensor pollicis longus et indicis proprius and flexor digitorum profundus, which are attached to the front dewclaw by 4 tendons (Figure 1). Each of those muscle/tendon units has a different function in movement. That means that if you cut off the dew claws, you are preventing the muscles that were attached to the dewclaws from functioning.
In contrast, rear limb dewclaws do not have muscle/tendon attachments, so their removal might be appropriate, except in the breeds such as Briards and Beauceron in which they should be retained.
Dewclaws Do Have Functions
If there are muscles and tendons attached to the dewclaws, then they most likely have a function. Broadly speaking, dewclaws have at least two different functions:
1. Grasp the ground when the dog is turning to prevent torque on the forelimb. Each time the front foot lands on the ground, particularly when the dog is cantering or galloping (see Figure 2), the dewclaw is in touch with the ground. If the dog then needs to turn, the dewclaw actively digs into the ground to stabilize the lower leg and prevent torque. In Figure 3 you can clearly see the dewclaw of a Corgi herding a sheep extended, ready to grip the ground. And in the image at the top of this article, you can see the dewclaws of a dog extended, ready to grip the water!
If a dog doesn’t have dewclaws, the leg will twist on its axis, creating increased pressure on the carpal bones, as well as the elbow, shoulder and toes. A lifetime of this kind of torque and the result can be carpal arthritis or injuries to and subsequent arthritis in other joints of the forelimb, such as the elbow, shoulder, and toes. Remember, the dog is participating in the activity regardless, so there will be concussive pressures on the leg, and if the dewclaw does not help to stabilize the leg, those pressures will be transmitted to other areas of the leg, especially the joints.
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Arguments for Removing Dewclaws
1. The dewclaws will get injured. This is the most common reason I hear for removing dewclaws. A friend of mine had such a severe dewclaw injury in one of her dogs that she swore she would remove them on all the dogs she bred subsequently.
But the data indicate that dewclaws are not injured very often. A study published in 2018 showed that the dewclaw was the LEAST likely toe to be injured in agility dogs, in which landing and turning from jumps and other obstacles put the toes at risk for injuries. Thus, it makes no sense to remove the dewclaws because of risk of injury. And, of course, no one would consider removing the 5th digits in the front feet, which are by far the most commonly injured toe.
2. Owners forget to trim the dewclaws. Surely this is a matter of education. Do we really want to remove a functioning digit in all dogs, just because some owners need to be reminded that they must be remember to trim the dewclaws?
3. Dewclaws make the forelimb look less straight when viewed from the front in conformation. The AKC states: “The breed standard describes the characteristics of the ideal dog to perform the function for which it was bred.” While we could have long discussions about the veracity of this statement, it is interesting to note that there are VERY few breed standards that require dewclaw removal. I know of only one – the Vizsla breed standard.
So, here’s a plea to retain dogs’ dewclaws. They are a functioning digit. They are the toe least likely to be injured. Isn’t this enough to convince us not to do the dewclaws?
Debra C. Sellon, Katherine Martucci, John R. Wenz, Denis J. Marcellin-Little, Michelle Powers, Kimberley L. Cullen. A survey of risk factors for digit injuries among dogs training and competing in agility events. J Am Vet Med Assoc 2018;252:75-83