Do the Dew(claws)?
A dog using its dewclaws, preparing to “grip” the water. Photo by Tom Fretz
As a veterinary sports medicine specialist, I work extensively with canine athletes, developing rehabilitation programs for injured dogs or dogs that required surgery due to performance-related injuries. I have seen many dogs, especially field trial/hunt test and agility dogs, that have chronic carpal arthritis, frequently so severe that they must be retired or at least carefully managed for the rest of their careers. I noticed that very few of those dogs had dewclaws and began to wonder whether these appendages might, in fact, protect a dog from injuries. What I learned might surprise you.
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.
Figure 1. Anatomical diagram viewing the medial side of a dog’s left front leg demonstrating the four tendons that attach to the dewclaw. Illustration by M. Schlehr, from Miller’s Guide to the Dissection of the Dog.
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.
Figure 2. In this galloping dog, the dewclaw is in touch with the ground. If the dog needs to turn to the right, the dewclaw will dig into the ground to stabilize the lower leg and prevent torque.
Figure 3. Corgi using its left dewclaw while herding. Photo by Jessica Viera.
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