Why Are My Old Dog’s Back Legs Collapsing?

As our dogs get older, you may notice subtle changes in their physical abilities.

While slowing down can be a normal part of aging, collapsing of the back legs is not a standard occurrence.

An old dog that is experiencing weakness of the limbs may have an underlying issue to blame, ranging from joint conditions to systemic illness.

In this article we will discuss the possible reasons why your old dog’s back legs are collapsing, and offer you some tips on how to bring your dog comfort throughout the process.

My Old Dogs Legs Collapsing

Is It Normal For My Old Dog To Develop Leg Weakness?

Our senior pups may not be as strong as they were in their prime, but it is not normal for their limbs to collapse out from under them.

The occasional slip and quick recovery may not be a cause of concern, but significant hind limb weakness can be a sign of something serious.

It is not normal for an old dog’s back legs to collapse, so this behavior should always warrant immediate concern on our part.

Why Are My Old Dog’s Back Legs Collapsing?

As we mentioned above, it is not normal for a dog to experience hind limb weakness.

Whether this is a gradual onset or it occurs suddenly, this is almost always the result of an underlying health concern.

To help you get to the bottom of your old dog’s leg collapsing, let’s list some of the most common causes below.


Arthritis is one of the most common ailments that impacts our senior furry friends.

This degenerative joint condition leads to a constant cycle of inflammation within the canine joints, causing the cartilage to become brittle over time.

The ends of each bone will begin to rub together without the support of healthy cartilage, leading to significant deterioration of the joint all together.

When the joints begin to deteriorate over time, the dog will begin to use the muscles in the region less and less.

Neglect of these areas can lead to muscle atrophy over time, causing the affected limbs to become weaker.

If their arthritis and associated weakness is severe enough, they may have a hard time standing.

Hip Dysplasia

Hip dysplasia is another common joint condition that can cause a dog’s back legs to collapse.

Hip dysplasia is a condition that refers to the abnormal formation of the hip joint, causing laxity in the hips as they grow.

This looseness will lead to the development of inflammation and boney spurs over time, causing the hips to grind with each step.

Not only is this extremely painful, but it can lead to the development of arthritis in the area.

Once this painful joint deterioration in the hips begins, a dog will begin to compensate for their pain.

They may put as little weight as possible on the back legs, leading to the atrophy of muscles in the area.

Similar to muscle atrophy in dogs with severe arthritis, this can cause significant limb weakness.

Not only can their legs collapse due to weakness, but they also may become so painful that they simply cannot get up on their own.

Intervertebral Disc Disease

Intervertebral disc disease (IVDD) is a condition that refers to the deterioration of the discs within the bones of the canine spine.

The discs within the vertebrae serve as a cushion between each bone, offering comfort and shock absorption with each movement.

Dogs with IVDD experience deterioration and hardening of these discs, making them prone to injury.

Once these discs start to deteriorate, they can begin to slip or bulge out of place.

This can cause the discs to invade the spinal cord space, leading to excruciating pain and potential paralysis.

One of the main signs of this complication is limb weakness, which is why this could be a potential cause of your old dog’s symptoms.

Degenerative Myelopathy

Degenerative myelopathy in dogs is a serious condition that impacts their motor abilities.

DM leads to the progressive deterioration of the white matter within the spinal cord, leading to a slew of motor complications to follow.

This condition most often impacts the hind legs, but it can affect the front limbs in some dogs as well.

DM in dogs is a common cause of sudden hind limb collapse in large breed dogs.

You may first notice subtle changes such as mild ataxia and swaying while walking, only for their coordination to rapidly deteriorate as the disease progresses.


Injuries can also be responsible for the sudden collapse of your old dog’s hind legs.

Not only can injuries to the spine or legs cause the weakness in itself, but injuries can also further aggravate a current joint condition they are experiencing.

For example, some dogs with IVDD will rupture a disc in their spine while jumping off the couch.

If you can tie your dog’s back leg collapse to a sudden injury that occurred, it’s very possible that the trauma is to blame.

Underlying Illness

While you may assume the cause of any leg collapse would be tied to bones and joints, this is not always the case.

Sometimes your dog’s hind limbs can collapse due to overall weakness, and many forms of systemic illness or chronic conditions can cause this.

Some unexpected underlying illnesses that cause weakness in old dogs include diabetes, Cushing’s disease, anemia, cancer, ruptured tumors, allergic reactions, and cardiac disease.

These conditions will typically generate other symptoms in addition to their back leg weakness, so it’s important to examine your pup for any other change in behavior.

When To See The Vet

As you can see, there are many reasons why your old dog’s legs may have collapsed.

Due to the varying possibilities on the table, we always suggest seeking veterinary guidance from the moment their symptoms begin.

Not only is it important to seek immediate care with a symptom as serious as limb collapse, but there is always a chance that your pup is in pain.

If you ever notice your pup struggling with decreased strength in their hind limbs, we always suggest giving your vet a call.

Final Thoughts

Our old dogs may begin to experience weakness in their hind limbs for many reasons.

If you ever notice your pup struggling with strength in their old age, we always suggest reaching out to your vet for further guidance.

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