Old Dog's Back Legs Giving Out: Causes and What to Do

When are a dog’s back legs giving out an emergency?

A dog whose back legs give out within hours or days needs a vet the same day, and one that cannot stand or leaks urine needs one now.

Merck Veterinary Manual describes the neurologic signs of a herniated disc as ranging “from a loss of motor control in the hind legs to paralysis and incontinence.” It says that in dogs with severe signs, “surgery must be performed promptly to relieve the pressure on the spinal cord,” and that recovery chances fall if surgery is delayed more than 24 hours after pain perception is lost.

Go now if your dog:

• collapsed or cannot stand
• drags one or both back legs
• leaks urine without noticing
• cries out when touched along the spine or neck

Tonight, keep your dog on a flat, padded, non-slip surface, limit movement and call the clinic. Say when it started and film the walk if you can.

Sudden or gradual: which causes fit?

Sudden weakness points to disc herniation, a spinal blood-vessel blockage or a wobbler flare. Gradual weakness over months points to degenerative myelopathy or osteoarthritis.

The table below sorts the causes that the Merck Veterinary Manual and Cornell pages describe. The “How urgent” column is this site’s editorial reading of those pages. The sources describe the diseases, and they do not grade urgency for an owner.

Cause	Onset	Typical signs (per source)	Pain?	How urgent
Disc herniation (IVDD)	Can be sudden; large breeds may worsen slowly	Loss of hind leg control, paralysis, incontinence; neck disc causes neck pain and spasms	Often	Same day. Surgery time-sensitive in severe cases
Fibrocartilaginous embolism (FCE)	Sudden, often after jumping or running	Abrupt change in gait; mild cases improve in 1 to 2 weeks, outlook poor if severe	No	Same day. MRI makes the diagnosis
Wobbler syndrome	Slow or sudden	Incoordination, odd stride, weakness in all legs, neck pain	May be	Prompt exam. Surgery often needed; about 80% do well with it
Diskospondylitis (spinal infection)	Not stated	Spinal pain, fever, low mood, weight loss; nerve signs can follow	Yes	Prompt exam. Antibiotics for at least 8 weeks
Spinal tumor	Progressive in the example given	Worsening partial paralysis of hind legs (nephroblastoma, mostly in young dogs)	Varies	Prompt exam and imaging
Degenerative myelopathy (DM)	Gradual, usually past age 8	Painless incoordination and weakness; trouble placing feet; scuffed hind toenails	No	Book an exam within days. No specific treatment
Osteoarthritis	Gradual	Slow to rise after rest, stairs hard, less jumping, muscle atrophy	Yes	Book an exam. Treatable, mostly with weight and pain control

Sources: Merck Veterinary Manual, spinal disorders, Cornell, degenerative myelopathy, Merck, osteoarthritis. Checked 2026-10-26.

Two limits apply. A dog can have more than one cause at once, since osteoarthritis is common in older dogs. And no one can tell these apart by looking, so the table is for deciding how fast to call, not for naming the disease.

What causes weak back legs in an older dog?

The main causes of weak back legs in an older dog are degenerative myelopathy, osteoarthritis and disc disease, with spinal blockages, infection and tumors less common.

Degenerative myelopathy. Cornell describes it as a progressive spinal cord disease, “typically affecting dogs around eight years of age or older.” Signs often start in one hind limb and spread to both. Cornell says dogs lose the ability to walk after six to twelve months, and may later show weakness in the front legs. Merck says there is no specific treatment and that most affected dogs are euthanized within one to three years. Cornell adds that routine physical therapy may delay progression.

Osteoarthritis. Merck’s professional manual says clinical signs usually go unrecognized until dogs are 5 to 13 years old, and that lameness “may be less apparent than expected” even in advanced disease on both sides. Slowness to rise after rest and trouble with stairs are the common signs.

Disc disease. Merck names Dachshunds, Beagles, Shih Tzus, Lhasa Apsos and Pekingese among the small breeds at risk. Merck says a herniated disc can cause severe signs suddenly, as early as one to two years of age, so disc disease is not only an old-dog problem.

Why does an elderly dog’s back leg muscle shrink?

Hind leg muscle shrinks in older dogs mostly because disease or pain makes them use the legs less, and the sources I checked name muscle atrophy as a sign of several causes.

Merck lists muscle atrophy as an exam finding in osteoarthritis and says pain and lameness develop “secondary to joint dysfunction or muscle atrophy.” Cornell lists muscle loss among the signs of degenerative myelopathy. Merck also says osteoarthritis may be present in up to 40% of dogs aged 8 months to 4 years, long before signs show.

What the sources did not give me is a dog-specific figure for pure age-related muscle loss (sarcopenia). Studies in dogs are fewer than in people, so this page makes no claim about how fast it happens. A vet can score muscle loss by feel along the spine and hips, and will ask what else is causing it.

What can I do at home for a dog with weak back legs?

Start with grip underfoot, then easier access to beds and cars, then a support harness, and keep the vet exam on the list.

This checklist follows the Dog Aging Project’s mobility guide (March 2021, by a veterinarian on its research team). The reasons are the project’s. It is not a treatment for any cause above.

Step	Why it helps
Rugs or mats with grip backing on slick floors, where the dog sleeps and walks	Add traction. Check they do not bunch up, since they become a tripping hazard
Limit running and jumping on hardwood and tile	Older dogs are more likely to be hurt doing these on slippery floors
Keep nails short	Short nails let the paw pads grip
Toe grips or rubber-gripped booties	Add traction where rugs are not practical
Pet stairs, or a ramp if even a few steps are hard	Let the dog reach couch, bed or car without jumping. Ramp surface needs grip
Support or mobility harness	Helps you lift or steady a dog that struggles to rise
Stroller or wagon when walking is no longer possible	Lets the dog go outdoors. Secure the dog and pad it to prevent pressure sores

The guide does not cover raised bowls, so this page does not recommend them.

Weight matters too. Merck calls weight optimization “the primary preventive method to slow development of OA in dogs” and says even very modest weight loss improves function in overweight dogs. Ask your vet for a target weight before changing food.

How do I lift a dog with hind leg weakness?

Use a support or mobility harness, and take advice from your vet on the style and size before you rely on one.

The Dog Aging Project says harnesses help owners lift or support a dog that struggles to get up, especially medium and large breeds. It says temporary hind-end aids are easy to use but not for constant wear, while full front-and-back harnesses can stay on longer. It advises asking your primary vet to choose the product, style and size.

If the weakness is new, or your dog cries out, do not lift until a vet has seen it. Disc disease and spinal infection can be painful, and a wrong lift can add strain. Our guides index lists other mobility and comfort pages as they go live.

What will the vet do about my dog’s back legs?

The vet will do a neurological exam and often imaging, because the cause decides the treatment.

Cornell lists neurological exam, blood work, X-rays, MRI or CT and spinal fluid analysis as ways to rule out other spinal cord diseases. Merck says FCE is diagnosed with MRI. For degenerative myelopathy, Cornell says no specific test exists in a living dog, so the vet rules out other causes first. Cornell adds that genetic testing can show whether a dog carries one or two copies of the risk variants.

Before the visit, write down when the weakness began, whether it was sudden, which legs are involved, any accidents indoors, and whether your dog yelps when touched. Bring a short phone video of the walk. For more on how this site checks its sources, see how we research.