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Why is My Dog Limping on their Back Leg?

By Josie F. Turner, Journalist specialized in Animal Welfare. Updated: September 2, 2018
Why is My Dog Limping on their Back Leg?

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Seeing someone limp could mean many things. Perhaps they have had a minor injury, did not stretch before exercise or are simply feeling the effects of age. In most cases, a person will be able to shine some light on the reason for their hobble. With dogs, providing an explanation may be somewhat harder. We may have noticed a gradual limp on their leg developing over time. It may be something which has seemingly appeared overnight. Even if you have witnessed an injury, you may not know what part of the leg is damaged and how best to treat it.

If you are wondering why my dog is limping on their back leg?, AnimalWised looks into the various causes of this condition as well as looking at different treatment methods. None of this is an adequate replacement from seeing a specialist. Instead, it might help you before you can visit one as well as improve the chances of making their limp a temporary condition.

You may also be interested in: My Dog is Limping on Their Front Leg

Anterior cruciate ligament rupture

You may know the anterior cruciate ligament in it's acronym form of ACL, especially if you are a soccer form. Often known as a football injury, tearing the ACL is also a typical injury in canine traumatology. The result is often a distinct limp in a dog's hind leg.

What is the anterior cruciate ligament?

A fibrous band located in the knee leading from the top of the femur to the tibia (the thigh bone to shin bone). Its purpose is to stop the bones from moving forward or inward when the knee is in action. There is another cruciate ligament known as the posterior cruciate ligament. The PCL is broader and stronger than the ACL. While it can still be damaged, it is not as vulnerable as the ACL due to its strength and placement, making a tear of the PCL a much less common injury. Along with the other two main ligaments of the knee, these both facilitate the right movement and help prevent the bones moving incorrectly to create injury.

Are there breeds more prone to ACL injuries?

There are two main types of dog which are more likely to receive an ACL injury. These are:

  • Small dogs with short legs: especially if they are in middle age or over, these breeds are more vulnerable to possible ACL injuries. The Shih Tzu and Pug are both breeds which fall into this category. An additional concern is that these dogs have the disadvantage of being prone to discolagenosis, a degeneration of the joint collagen which predisposes them to such problems.
  • Large dogs: these large dog breeds include the Labrador, Rottweiler and Neapolitan Mastiff.

However, any dog may suffer an injury to or rupture of their anterior cruciate ligament. Dogs which engage in strenuous exercise without building up to it, awkward jumping onto surfaces or rotating when standing may receive an injury to this ligament.

How to distinguish limp caused by ACL injury

Most often, lameness in the hind leg caused by rupture of the ACL is due to an abrupt injury. It can be very painful and will likely cause your dog to walk without putting any weight on the hind leg or to only gingerly place weight on it. When standing, they will hold their leg bent so that it raises up into the air or extend it away from their body. These are both ways to relieve tension in the knee and therefore reduce the pain symptoms.

Inflammation may appear on the knee, but it is not always seen. All symptoms of a torn ACL will depend on the intensity of the injury, whether completely torn or partially ruptured.

How is a rupture of the anterior cruciate ligament diagnosed?.

The ways to diagnose an ACL injury will depend on the individual dog. If a ruptured ACl is likely, the vet will carry out a ‘drawer test’ during which the tibia is moved forward with the femur in place. If the ligament is broken, the tibia will move far without much resistance as the ligament is not holding it in place properly. It is also likely the dog will be sedated as without anaesthetic, this can be a very painful procedure.

A radiograph may not confirm a rupture, but it can show the signs of osteoarthritis which appear in the first weeks after a torn anterior cruciate ligament. The articulation of the knee will begin to degenerate, making the joint surfaces irregular and worsening the prognosis. This is why going to the vet early to detect an injury is so important. In more complicated cases, and subject to availability in a given clinic, an arthroscopy or MRI may be used.

How to treat ACL injury in dogs

There are two main types of possible treatment for ACL injuries in dogs:

  • The conservative medical treatment approach is for those which are not deemed acute enough to require surgery. Physiotherapy rehabilitation measures are proposed. These may include water movement classes or even laser therapy, both designed to reduce inflammation. Additionally, a specific diet will be implemented so that they do not gain weight (or become obese) due to lack of mobility as well as promoting the regeneration of articular cartilage and delaying arthrosis as much as possible. They will indicate some recommendations for daily exercise as well as avoiding terrain which may cause more damage. These include slippery floors (e.g. tiled kitchen floor), ramps and steps.
  • Surgery may be employed if the case is severe enough. It is only used when necessary, not only due to expense, but also the difficulties in recovery. Any sudden movement from your dog could result in more damage, so they will have a bandage for their entire leg and will need as much rest as possible. As with a more conservative course of treatment, proper diet will need to be implemented to ensure they don't gain weight and have as much chance of a full recovery as possible.

It should be pointed out that sometimes the other hind leg will suffer the same fate after a few months. This is because if one leg has become injured and the dog continues to walk, the other leg will have all of its weight put upon it. If we leave it late and go to the vet later rather than sooner, it can serious affect the prognosis. It is not uncommon for the other anterior ligament to break, especially if the dog is aged.

Why is My Dog Limping on their Back Leg? - Anterior cruciate ligament rupture

Dislocated kneecap

The patella is the kneecap and it is lodged in between the trochleas of the femur in a specially created groove. When in proper alignment, it can be moved up and down, but not to the right or left. If you look as someone flexes their knee, you will see the patella moves only in this direction.

However, if the knee dislocates you will see that the patella moves laterally or medially. This can happen for two main reasons:

  • Congenital: this means that from birth the natural lodging of the patella is defective and may move at will. It usually affects breeds such as the Toy Poodle, Pekingese or Yorkshire Terrier. It is often one of the many congenital defects these breeds may be affected by, especially in terms of bone structure. Legg-Calvé-Perthes disease is one other example. You will likely notice a dislocation when the dog is jumping or if they hold the affected leg in the air when climbing steps, but then return to normal on level ground. We may think this is just the awkward movement of a puppy, but it should be noted to a vet as the earlier the treatment the better the prognosis.
  • Trauma: if a dog is hit by a car, has a fall or sustains any sort of traumatic injury to the knee, their patella can become dislocated.

The degrees of dislocation are variable. Minor dislocations may repair by limiting exercise and incorporating other elements of physiotherapy. Large breeds are not unaffected by dislocation and a variation of dislocation called patellar luxation can occur in giant breeds. This is why vets need to be consulted so that we can know the right treatment to undertake.

What tests can be done?

Tests to determine patellar dislocation and determine why your dog limps on its hind leg are usually:

  • Basic examination - the knee ‘creaks’ under manipulation.
  • Radiograph detects signs of osteoarthritis or rupture to the trochleas of the femur.
  • Arthroscopy or MRI.

Although the vet may make the diagnosis of a dislocated knee, the risk of osteoarthritis needs to be considered. This is because the dislocated kneecap can rub on the surface of the femur and lead to wear and tear which is essentially irreversible.

There are some surgical techniques which can range from a relatively simple procedure (such as deepening the groove between the trochleas of the femur) to more complicated endeavors (like repositioning a piece of the anterior part of the tibia to relieve tension). The type of surgical treatment depends on the individual dog and the nature of their dislocation.

Why is My Dog Limping on their Back Leg? - Dislocated kneecap

Hip dysplasia

Hip dysplasia is a common canine ailment which can be exacerbated by many different causes, but the root cause is genetic. Essentially, the head of the femur does not fit into corresponding socket in the pelvis. It is a genetic condition, but may only be activated by some environmental or lifestyle factor. This is why it is particularly cruel to allow a dog with genetic hip dysplasia to give birth as it will inevitably cause them great pain.

There are some breeds which are more affected than others such as the Labrador, Spanish Mastiff or Bordeux Mastiff. There are several degrees of dysplasia with mild cases often going unnoticed at first by their owners. However, in moderate to severe cases, symptoms should be noticeable at around 5 to 6 months of age. The dog will walk with a wobble at the hips. Over time, the top of the femur will rub against the acetabulum (the socket of the pelvis where the joint meets). This can lead to arthritis or osteoarthritis. This is why you may see a limp in your dog's hind legs and is often a lameness which can be seen on both sides. It can also lead to the complete breakage of the ligament connecting femur and pelvis, leading to a serious and debilitating condition if it occurs.

In addition to the oscillating gait we may detect as they walk, symptoms can include:

  • Difficulty to commence walking after a state of rest
  • Muscular stiffness
  • Resistance to movement, especially down and up stairs
  • When the degeneration is acute, complete lameness in the hind legs can occur, making walking impossible

Treatment of hip dysplasia in dogs:

The treatment can be complicated, but rehabilitation and physiotherapy is usually implemented in milder cases of hip dysplasia. This will be coupled with a quality diet designed to improve joint and bone strength. Avoiding excess calcium is important, especially in giant dog breeds which undergo rapid growth. Anti-inflammatories and cartilage protectors, such as hyaluronic acid and chondroitin sulfate, can help reduce its progression and improve symptons.

In severe cases, hip dysplasia may only be corrected by surgery. There are multiple techniques, all of which are complicated. These can include arthroplasty which involves excision of part of the head of the femur or a triple pelvic osteotomy. The former is only for small to medium sized dogs while the latter is an aggressive intervention which should only be used when there is no other way to help a dog walk again. The latter in particular is expensive and should only be carried out when no other type of surgery will suffice. A titanium prosthesis which replaces the head of the femur is often very successful, but prohibitively expensive for most dog owners.

Why is My Dog Limping on their Back Leg? - Hip dysplasia

Panosteitis

The term panosteitis translates literally to ‘inflammation of an entire bone’. Pain is caused by the inflammation of the outermost layer which covers the bone (periosteum) and its cause is relatively unknown. Genetics seem to play some part, but can be exacerbated by other factors.

It is much more frequent in dogs which grow rapidly, usually large or giant breeds which undergo a lot of development between the ages of 5 and 14 months. They most commonly affect the long bones like the femur, hence why they may cause a limp in the hind leg of a dog.

It can appear in both acute and mild cases. It is treated with the use of anti-inflammatories, a careful diet, a regimen of light exercise and, above all, rest.

Avascular necrosis of the femoral head

Avascular necrosis of the femoral head (the head of the femur) is also known as Legg-Calvé-Perthes disease and it is a possible reason for your dog's hind leg limp. It usually affects mini or toy breeds of dog such as the Mini Pinscher, Toy Poodle or Yorkshire Terrier. It is sometimes confused with hip dysplasia.

It occurs due to the head of the femur not receiving enough blood flow at a critical stage. Necrosis, or unplanned cell death, sets in and after 4 to 9 months we might see the following symptoms:

  • Marked lameness
  • Atrophy of the muscles
  • Shortening of the affected leg (due to muscle atrophy)
  • Crepitations (rattling sound) when moving
  • Pain

Is it hereditary?

Until recently, this disease being hereditary was the only explanation. However, it is now believed to be caused by microfractures in the area producing a drastic reduction in blood flow and leading to necrosis of the femoral head and neck. The small size of the breeds most commonly affected must surely predispose them to this disease.

Its treatment is surgical and involves the excision of the affected parts of the femoral head. Small dogs means recovery usually looks good and facilitates a relatively easy surgery.

Other causes of limping in the hind leg

There are dozens of possible causes of lameness or limping in a dog's hind leg. If you still don't know why your dog is limping on their back leg, it could be one of the following:

  • Osteosarcoma: this is the most common forms of bone cancer in dogs and one of the most malignant. It generally affects medium-large sized dog breeds who are young, but can affect a dog of any size or age. It is most commonly found in the back leg, typically behind the knee, the distal part of the femur or the tibia. Once diagnosed by a histopathology, amputation of the limb is mandatory and the dog will need chemotherapy since it metastasizes with ease. Affected dogs may only have a few months to live, but this can be lengthened with the correct care.
  • Fractures in metatarsals and phalanges: you may not think of your dog having ‘fingers’, but they have these parts of their paw which are prone to damage, especially as puppies. Sometimes it is a simple fissure which can mend on its own. However, fractures can occur which need splints or casts to fix. Anti-inflammatories are also used, but surgery is not recommended unless necessary.
  • Paw pad injury: cuts, irritations or other types of wound can affect the paw pads of a dog. If this is the case, their hind back leg of the affected paw may hurt when pressure is exerted on it. If so, it can result in a limp in their back leg or legs.
Why is My Dog Limping on their Back Leg? - Other causes of limping in the hind leg

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Why is My Dog Limping on their Back Leg?, we recommend you visit our Other health problems category.

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Isaura Neumayer
My dog was taken to get his nails shorten and bathed when I picked her up she has been limping, I will be taking her back to petsmart banfield so they can look at her

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