Watching a dog age is often bittersweet. Their muzzle whitens, their pace slows, and it might be a little harder for them to head up and down the stairs. Yet sometimes more concerning health changes can emerge, and they can catch owners off guard. 

One of those diseases is called degenerative myelopathy (DM); it’s a progressive disease of the spinal cord that leads to muscle weakness and eventual paralysis. Though painless, the loss of mobility it causes can be devastating for both dogs and their families. Scientists have traced the strongest genetic connection to a mutation in the Superoxide dismutase 1 (SOD1) gene, yet environment and age also shape how the disease unfolds.

The Genetics of Degenerative Myelopathy

Degenerative myelopathy is primarily regarded as a genetic condition. The SOD1 gene, which normally produces an antioxidant enzyme to neutralize harmful molecules in cells, is central to the disease. In healthy dogs, the enzyme converts reactive oxygen species into less harmful compounds, protecting delicate cells from oxidative stress.

A mutation in the SOD1 gene disrupts this process, leaving cells vulnerable. Over time, this contributes to the deterioration of motor neurons in the spinal cord. When those neurons falter, communication between the brain and muscles weakens, leading to the hallmark mobility issues seen in DM.

Genetic testing has shown that the highest risk occurs in dogs with two copies of the SOD1 mutation—known as homozygous carriers. These dogs have inherited one risk variant from each parent. Even so, not every dog with this genetic profile will develop clinical DM. This suggests that while the mutation raises susceptibility, additional factors influence whether and when the disease manifests.

Recognizing the Signs of Degenerative Myelopathy

Because DM develops gradually, the earliest signs can be easy to miss. Unlike arthritis or spinal disc disease, degenerative myelopathy does not cause pain. Instead, it starts with coordination problems.

• Early stage: The hind legs show slight weakness. Dogs may stumble or drag their back paws, wearing their nails unevenly. Owners sometimes notice “knuckling,” where a paw bends under so the top of the foot scrapes the ground.
  

• Progression:Weakness intensifies. Standing up becomes difficult, stairs a challenge, and a once-smooth gait turns into a wobble. Dogs may cross their back legs awkwardly as they walk.
  
  

Advanced stage: Paralysis sets in. Hind legs eventually stop working, and some dogs lose bladder and bowel control. In the most advanced cases, the disease moves forward to affect the front limbs and even the muscles needed for breathing.

Because these symptoms overlap with other conditions like arthritis, slipped discs, or hip dysplasia, veterinary evaluation is essential for proper diagnosis. A clear picture often requires both genetic testing and clinical assessment.

Caring for a Dog With Degenerative Myelopathy

There is no cure for DM, but management can improve quality of life and extend mobility. Supportive care focuses on maintaining strength, reducing injury risk, and adapting to the dog’s changing needs.

• Exercise and therapy: Controlled activity, such as swimming or guided walking, helps preserve muscle strength without straining weakened limbs. Physical therapy guided by a veterinarian can slow decline.
  

• Assistive devices: Harnesses, slings, and wheeled carts can restore mobility and independence, especially in middle and late stages.
  

• Home adjustments: Non-slip flooring, ramps, and easy access to resting areas reduce daily stress.
  

• Veterinary partnership: Regular checkups allow vets to monitor progression and recommend supportive treatments or therapies tailored to the individual dog.

Early recognition and supportive care may help dogs stay active and comfortable for longer, even as the disease progresses. Read more on how to keep your dog vibrant in their Senior years and how diet can shape their biological health.