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Knuckling: A Dog Walking on the Top of Paws

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Dog Walking on the Top of Paws

A dog walking on the top of paws (often referred to as knuckling) may be suggestive of some type of degeneration of the nervous system. Finding out the source of the problem is something only a vet can do through a thorough neurological exam along with diagnostic testing. It's best to see the vet sooner than later when a dog is walking on the tops of paws because some medical conditions may progress rather quickly. In some complicated cases, the vet may refer to a veterinary specialist specializing in veterinary neurology.

Joelmills, Wikipedia CC BY-SA 3.0

Joelmills, Wikipedia CC BY-SA 3.0

Conscious Proprioception Response

It is natural for dogs to keep their feet down on the ground with their paw pads making contacting with the floor. Dogs will make a conscious effort to avoid dragging the top of their paws on the ground when they are walking. The medical term for this conscious effort is conscious proprioception response. Some people may call it a reflex, but it's rather a response because it involves a certain degree of conscious control.

Evoking the conscious proprioception response is part of a vet's neurological exam. The response is proof that the dog's nervous system is working as it should. In an ideal situation, the dog should promptly return the paw to its normal position after the vet has turned the paw upside down.

A delay or a lack of response therefore can be indicative of some type of neurological deficit affecting the dog's central nervous system. The picture on the left shows a dog who is not exhibiting the response.

It is therefore understandably a problematic sign when a dog's toes are dragged on the ground when walking. When you see a dog walking on the top of the paws with the toes being dragged on the ground, it's referred to as knuckling. 

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A Lesson in Anatomy 

In order to better understand what may be going when a dog is walking on the top of the paws, it helps taking a closer look into a dog's anatomy.

A dog's spinal column is basically a cable that contains a bundle of nerves that relay information between the brain and the rest of the body. In particular several small nerves that branch off the dog's spinal column are responsible for allowing a dog to feel and move the extremities (front and rear legs).

A dog walking on the top of the paws is therefore a dog who has lost perception and feeling of his toes and the dog ends up walking on the top of the paws. This loss of perception is indicative of some sort of loss of communication between the dog's nerves supplying the dog's extremities and the brain. This loss of communication is therefore preventing the dog from flipping his paw as he should.

Causes of dog hallucinations

Causes of Dog Walking on the Top of Paws (Knuckling)

A dog walking on the top of paws is likely to be suffering from some type of nervous system disorder, but exactly of what type? There can be several predisposing factors.

Compressed Disc in the Spine

The medical term is intervertebral disc disease. What happens in this condition is that one or more of the discs that work as cushions between the dog's vertebrae, herniate and end up compressing the nerve roots causing a variety of symptoms such as neck or back pain and paralysis.

The brain still intends to command the muscles of the dog's extremities, but is unable to get the muscles to contract due to this disruption in communication deriving from the compressed nerve roots. The affected dogs therefore end up dragging their legs and toes and may sit with the legs tucked under in an unusual fashion.

X-rays are not very helpful in diagnosing this condition. A better option (yet, much more costly!) is a CT scan, MRI, or a procedure called a myelogram.

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Presence of A Tumor

spinal cord dog

Any type of mass that ends up enlarging and compressing the spine by the base of the neck to the back can play a role in causing a dog walking on the top of the paws (knuckling.) Bone tumors may sometimes arise in the dog's vertebrae.

Another possibility is the presence of tumor affecting the lymph node system. An enlarged lymph node in this case may be exerting pressure on the nerves of the affected leg.

In some cases, a brain tumor may be responsible for causing a dog to be standing with a paw that's upside down. A brain tumor often arises secondary to some other tumor. For example, a dog with breast cancer may develop a brain tumor due to this tumor's tendency to spread to other locations (metastasis).

An Orthopedic Problem

In a dog walking on top of paws, it's important to notice if it's both paws or only one paw. If it's only one paw, there may be chances that the affected leg may have sustained some injury of some kind. For example, in a dog having problems walking on a front paw, so much so that the leg appears paralyzed, there may be radial nerve damage at play. This is nerve damage to the dog's radial nerve. 

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In some cases, a dog dragging the top paws of the rear legs may be suggestive of severe arthritis at the lumbosacral junction (where the lumbar spine attaches to pelvis) that has progressed to such an extent to affect the nerves that supply the hind legs.

A Metabolic Disorder

Sometimes the dog's liver may cause neurological signs. Basically, if there is some type of liver dysfunction going on, the liver may be unable to rid the body of toxins and this can lead to the build up of toxins in the blood resulting in neurological symptoms. Generally, affected dogs develop yellow-colored gums, eyes and skin of the ears (jaundice) along with neurological signs.

A dog with back pain may lose sensation in the rear legs.

Back legs crossing is a sign of DM

Degenerative Myopathy

Degenerative myopathy is a condition that is very common in German Shepherd Dogs but is also found in Pembroke Welsh corgi, Cardigan Welsh corgi and several other breeds.

Affected dogs develop progressive weakness and incoordination of the hind legs which then leads over time to complete paralysis. An initial sign may be a dog walking on the top of paws.

In the picture on the left you can see a corgi with DM. Notice the unusual leg crossing of the hind legs.

Presence of Blood Clot

While this is not very common it can occur sometimes. In this case, what happens is that a blood clot from a major vessel that supplies that leg causes blood flow to stop. A warning sign of this is a dog walking on the top of paws or giving any signs of lost function of the leg and the leg and paw feel very cold. This is something that requires immediate emergency treatment.

Time is of the Essence 

A dog walking on the top of paws is something that requires attention. If your dog is showing signs of lack of perception of the paws, you should see a vet as soon as possible. As seen, there are certain medical conditions that can cause permanent loss of nerve function. Some conditions can be managed through passive range of motion exercises, massages while doggy boots or socks may help prevent wounds on the surface of the paw, suggests Dr. Laura Devlin, a board-certified Veterinary Practitioner.

Photo Credits:

  • Diagram showing a tumour causing spinal cord compression, Cancer Research UK / Wikimedia Commons CC BY-SA 4.0
  • Joelmills Proprioceptive deficit ("knuckling over") in a ten year old German Shepherd Dog with suspected degenerative myelopathy CC BY-SA 3.0

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