When a dog begins to age, it’s common for physical symptoms to come to the forefront. This can leave a dog in a state of struggle as it looks to maintain its daily routine while battling the discomfort and pain.
As a dog owner, it’s important to look for specific signs of a dog’s health declining as it ages.
This can include paying attention to a dog’s legs. If you notice an old dog’s back legs collapsing, it’s important to take action.
A dog’s back legs can collapse due to hip dysplasia, muscular weakness, arthritis, spinal conditions, and/or degenerative diseases. These conditions are more common in older dogs as their bodies begin to decline.
Each condition has a unique set of treatment options and it’s recommended to consult with a vet as soon as you notice an old dog’s back legs collapsing.
Here are a few reasons why an old dog’s back legs collapse.
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Reasons Old Dog’s Back Legs Are Collapsing
1. Arthritis
Older dogs are prone to having arthritis.
This condition refers to the dog’s joints beginning to swell and become tender. Most dogs will become rigid and not move as much due to the natural discomfort of the condition.
When this happens, the rear legs can start to collapse. A dog won’t have the ability to generate force from its rear legs and this can amplify the pain as it moves.
This condition will get progressively worse with age and it’s essential to have the dog on a treatment regimen as soon as possible.

2. Muscular Weakness
Older dogs will lose muscle strength with age.
This is normal and it often has to do with the muscles losing their potency and overall flexibility. When this occurs, the dog will start to find it harder to run fast or get to where it needs to smoothly.
This can leave a dog anxious and unhappy, especially when the condition is rapidly deteriorating.
A lot of dogs will lose strength in specific muscles and that can include the rear legs. A senior dog’s rear legs collapsing can often be a sign of this type of weakness.
3. Degenerative Disease
Degeneration is possible in older dogs.
This refers to a condition where the joints and/or muscles become progressively weaker. The tissue around the muscles gives out and that can lead to significant pain, discomfort, and sometimes injury.
The goal is to diagnose where the degeneration is occurring and then begin to treat it. While the condition might not be easy to cure, it can be managed with the help of medication.
This is a common issue that is seen with senior dogs with collapsing rear legs. You will eventually find out the degeneration process has started and it is uncomfortable.

4. Hip Dysplasia
When the hips begin to give out, this is a serious concern for dogs.
This condition refers to the hip socket not offering comprehensive coverage when it comes to the ball and upper thighbone. This can cause the hip joint to become unstable and easy to dislocate as the dog moves around.
Many dogs will receive treatment for a hip condition such as this one because it can have a significant impact on a dog’s quality of life.
When the hip begins to give out, it is the rear legs that are impacted the most. This is why a dog’s rear legs start to give out.
5. Spinal Issues
If a dog has been injured, its spine might become compromised.
This will lead the dog to display sudden bouts of collapsing whether it is the front or rear legs. A lot of pressure is put on the legs when a dog moves and any type of spinal issue will cause them to stop functioning properly.
vets need to look into the spinal issue and begin working on the treatment regimen. This is the only way to help a dog get stronger as it battles the spinal condition.

6. Cancer
This is not as common in older dogs but it is something to be on the lookout for.
In essence, if a tumor grows along the spine or the rear legs, it’s possible it can start to impede a dog’s mobility.
This happens in different ways with some dogs suffering from pain while others not being able to move the way they used to. In one scenario, a dog’s rear legs might collapse as it tries to move around.
This is a sign you will want to go to the vet for more information.
They can pinpoint whether or not a tumor is there and if it needs to be removed.
7. Injury
This is often seen in dogs of all ages.
The rear legs are a part of the body and need to be assessed in great detail based on how the dog is feeling.
If a dog has been injured, it is possible the legs won’t function as they used to. This can be due to a fracture or ligament tear that has taken place. Sometimes, these injuries are not visible due to a lack of bleeding.
You will need to get an x-ray done to see what has gone on with the dog’s health and what needs to be done next.

8. Myasthenia Gravis
This is an autoimmune disease that can impact a dog’s nervous system. The nerves don’t fire as they normally would due to a block between the neurons and the muscles.
It is common for dogs to struggle with moving around when suffering from this condition.
Dogs will often be placed on a long-term treatment plan when facing this condition. It might also require therapy to help the dog strengthen its muscles.
9. Tick Paralysis
This condition refers to a type of poisoning caused by an attached tick.
When the tick leeches onto the dog, it will start to impact its ability to move. This can cause paralysis in specific parts of the body including the rear legs.
It’s essential to speak to a vet and find where the tick is. By removing the tick, this condition will get better and the rear legs won’t collapse any longer.

Final Thoughts
These are the main reasons an old dog’s back legs are collapsing.
Whether it is cancer, muscular weakness, or a simple sign of aging, a dog’s back legs collapsing is not normal. It’s recommended to consult with a vet to learn more about what needs to happen next.
Treating this condition is a must to ensure the dog’s quality of life isn’t impeded.
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