When your senior dog starts wobbling in the back end, the two most likely culprits are degenerative myelopathy and arthritis — and they look frustratingly similar at first glance.

Quick answer: Degenerative myelopathy (DM) and arthritis both cause rear-end weakness and difficulty rising in senior dogs, but they differ in one critical way: arthritis is painful and DM is not. A dog with arthritis will typically yelp, flinch, or resist being touched around sore joints. A dog with DM shows progressive weakness without pain signs — and over time develops knuckling, paw dragging, and loss of coordination. Getting the diagnosis right matters because the treatment paths are completely different. A veterinary neurological exam and, in many cases, an MRI are needed to tell them apart with confidence.

If you’re watching your older dog struggle to get up from his bed, slip on the floor, or lag behind on walks he used to love, you’re probably terrified. And you’re probably Googling at midnight trying to figure out what’s happening. I’ve talked with so many owners in exactly that spot, and the DM vs. arthritis question comes up over and over — because the surface symptoms overlap enough to make it genuinely confusing.

This article is my attempt to lay it out clearly: what the two conditions share, where they diverge, why the distinction changes everything about treatment, and when you need to push harder for answers.

What Do DM and Arthritis Have in Common?

Both degenerative myelopathy and arthritis commonly present in senior dogs with rear-end weakness, reluctance to rise, reduced stamina on walks, and general slowing down. This symptom overlap is exactly what makes early differentiation so difficult.

Both conditions tend to be progressive. Neither resolves on its own. And both predominantly affect older dogs, which means a dog who’s seven, eight, or ten years old presenting with hind-limb problems could realistically have either one — or, frustratingly, both.

Here’s the overlap you’ll likely see:

  • Difficulty rising from rest: Both arthritic dogs and DM dogs struggle to push themselves up from lying down
  • Rear-leg weakness: Both cause the back end to look weaker or less coordinated than the front
  • Reluctance to climb stairs or jump: Both make elevation changes harder and less appealing
  • Reduced activity: Both lead to a dog who seems less engaged, tires faster, or hangs back on walks
  • Muscle loss over the hindquarters: Both conditions, over time, contribute to visible muscle atrophy in the rear
Symptom Overlap at a Glance
  • Rear-end weakness or instability
  • Trouble rising from lying down
  • Reluctance to use stairs, ramps, or jump
  • Gradual loss of muscle over the hips and thighs
  • Progressive worsening over weeks to months

How Do DM and Arthritis Actually Differ?

The single most important difference between DM and arthritis is pain. Arthritis is painful; DM is not.

That one distinction cascades into a range of observable differences that, once you know what to look for, can help you have a much more informed conversation with your vet.

The Pain Question

A dog with arthritis will usually tell you he hurts. He may flinch or cry out when you press on sore joints. He may resist having his hips or hocks touched. He may guard his posture, hunching or shifting weight away from painful areas. Many arthritic dogs are visibly stiffer first thing in the morning and loosen up after moving around for a few minutes — this “warming up” pattern is a hallmark of joint pain.

A dog with DM, in contrast, typically shows no pain signs. He may look confused by his own body, but he won’t yelp when you palpate his spine or hips. He won’t flinch. This painlessness can actually fool owners into thinking the problem isn’t serious — but it’s actually a neurological red flag.

Coordination and Knuckling

DM affects the spinal cord, which means the signals between the brain and the back legs start breaking down. One of the earliest and most telling signs is knuckling — where a dog walks on the top of his paw rather than his pads because he can’t feel or correct his foot placement. You may also see a general lack of coordination or a “drunk” quality to the rear-end gait.

Arthritis doesn’t cause knuckling. It causes a shortened stride and stiffness, but the neurological pathways are intact. The dog knows where his feet are; the joints just hurt to use.

Progression Pattern

Arthritis tends to have good days and bad days, especially related to weather, activity level, and rest. DM is relentlessly progressive and doesn’t improve with rest or anti-inflammatories. If you trial your dog on pain medication (under vet supervision) and see meaningful improvement, that points strongly toward arthritis. If the weakness continues to worsen despite pain management, DM becomes a much more serious concern.

Signs That Point Toward DM Over Arthritis
  • Weakness continues progressing despite NSAIDs or pain medication
  • No flinching, yelping, or pain response when you touch the spine or hips
  • Dog knuckles over on one or both back paws
  • Loss of coordination — rear end seems to move independently of the front
  • Paws wearing unevenly or developing scrapes on top

Why Getting the Right Diagnosis Matters

If your dog has arthritis, the focus is on pain management, joint support, and keeping him comfortable — things like NSAIDs, joint supplements, weight management, and controlled exercise. These are genuinely helpful interventions.

If your dog has DM, none of those things will slow the neurological progression. What matters in DM is physical therapy and exercise, which many rehab specialists believe may help slow the rate of functional decline. The focus shifts entirely to maintaining muscle mass and mobility for as long as possible — and starting that early matters. You can read more about that approach in the DM Dog Exercise & Physical Therapy: Stage-by-Stage Guide.

Misdiagnosing DM as arthritis and treating only pain means the window for proactive physical therapy gets smaller while the disease advances. That’s a real cost.

Weight management is one intervention that genuinely helps both conditions — excess weight stresses arthritic joints and makes it harder for a weakening DM dog to carry himself. So if your vet hasn’t addressed body condition, that’s worth discussing regardless of diagnosis. The Nutrition & Weight Management for DM Dogs article goes into that in more detail.

A well-fitted rear support harness can also make daily life more manageable during the diagnostic period. Owners in the DM community often rely on a sling or rear harness to help their dogs get around safely while a diagnosis is being sorted out.

Helpful Steps While You Wait for Diagnosis
  • Keep a symptom diary — note good days, bad days, and any changes in gait or posture
  • Video your dog walking on a hard floor from behind — this is invaluable for your vet
  • Try to note whether stiffness improves after gentle movement (more suggestive of arthritis)
  • Ask your vet about a short NSAID trial — response or non-response is diagnostically useful

When Should You Push for a Neurological Workup?

You should ask for a referral to a veterinary neurologist when weakness continues to progress despite pain management, when your dog is knuckling or dragging paws, when there’s no obvious pain response, or when your general practitioner isn’t confident in the diagnosis.

This isn’t about doubting your vet — it’s about the fact that differentiating DM from other causes of rear-end weakness requires ruling out conditions like spinal cord compression, disc disease, or spinal tumors. Those conditions require imaging, typically an MRI, to identify. A neurologist will do a thorough neurological exam that tests reflexes, proprioception (the dog’s awareness of where his feet are), and pain sensation in a systematic way that goes well beyond what a general exam covers.

It’s also worth knowing that DM cannot be definitively confirmed in a living dog through any single test. Diagnosis is made by ruling out other causes. The SOD1 genetic mutation test can indicate increased risk, but a positive test doesn’t confirm clinical DM, and a negative test doesn’t fully exclude it. What imaging and a neuro exam do is rule out the treatable things — disc disease, tumors, joint disease — so you’re not missing something that could be addressed.

If your dog’s breed is on the higher-risk list for DM (German Shepherds, Corgis, Boxers, and several others), that context matters when you’re deciding how hard to push for a workup.

For a deeper look at DM stages and what the progression typically looks like once a diagnosis is in hand, the DM Stages in Dogs: Timeline, Symptoms & What to Expect article is a useful next read.

Go to Your Vet Promptly If You See
  • Sudden onset of weakness or inability to use back legs
  • Loss of bladder or bowel control alongside leg weakness
  • Dog falling over or unable to maintain a standing position
  • Rapid progression over days rather than weeks

Watching your dog slow down is one of the hardest parts of this whole journey. The not-knowing is often the worst of it. Whatever the answer turns out to be, you’re asking the right questions — and that matters more than you might realize right now.

Frequently Asked Questions

Can a dog have both DM and arthritis at the same time?

Yes, and this is actually fairly common in senior large-breed dogs. The two conditions can coexist, which is one reason a thorough veterinary workup is so important. Treating only arthritis in a dog who also has DM means the neurological decline will continue unaddressed.

Is degenerative myelopathy painful for dogs?

Degenerative myelopathy is generally considered a painless condition. The spinal cord degeneration causes progressive weakness and paralysis, but dogs typically do not show pain responses. This is one of the key clinical differences from arthritis, where pain is usually present and observable.

What breed of dog is most likely to get DM?

German Shepherds are most commonly associated with DM, but the condition occurs across many breeds including Pembroke Welsh Corgis, Boxers, Chesapeake Bay Retrievers, and Rhodesian Ridgebacks. A genetic mutation in the SOD1 gene is linked to DM risk and can be tested for.

What test confirms degenerative myelopathy in dogs?

There is no single definitive test for DM in a living dog. Diagnosis is based on ruling out other causes through MRI, spinal fluid analysis, and sometimes genetic testing for the SOD1 mutation. A confirmed DM diagnosis is technically only possible on post-mortem spinal cord examination.

This guide is based on real experience and should be used alongside professional veterinary care. Always consult your veterinarian before starting any new treatment or making changes to your dog’s care plan.