If your dog won't put weight on his back leg, you are rightfully concerned, dog's don't go limping like that unless there's a good reason to. When it comes to orthopedic problems in dogs, not bearing weight is indeed a red flag and veterinary receptionists in busy animal hospitals are often trained to give out the earliest appointments to owners of dogs who cannot bear weight on their legs, versus those who can. "Is your dog able to put weight on his leg?" is therefore an important question that can differentiate a dog who needs immediate attention from one that can wait perhaps another day or two.
A Sign of Severe Pain
Sure, dogs who are limping are in pain, there's no bones about that, but dogs who are limping and can't even bear to put some weight on their back leg, are likely to be in more severe pain and deserve immediate vet attention. Fortunately, dogs have four legs and they can therefore compensate with their other legs, but just because a dog is still mobile, doesn't mean that he is feeling OK.
Spared from the gift of talking, it's important to be a dogs' ambassadors. Vets often hear dog owners say things like: "My dog won't put weight on back leg, but doesn't seem to be in any pain" but this is not a good observation. Just because a dog is not yelping, moaning or groaning, doesn't mean he's not in pain!
Vocalizing is something humans mostly do, and dogs are very discreet in manifesting pain through vocalizations. Sure, dogs may yelp when a person ends up stepping on their foot or when they end up walking on some sharp glass, but often other types of more chronic, ongoing pain are not manifested vocally at all, other than by limping. So if a dog limps, it's a sure sign of pain and not bearing weight on a leg can actually be a sign of severe pain.
The Lifting Test
There is a test dog owners can do at home to better assess the situation. Even though this test might not be 100 percent accurate, it can give a rough idea about the severity of the dog's pain.
To do this test, the rear good leg should be lifted up off of the floor so that the dog must put weight on the leg that hurts. When this happens the dog may put weight on the leg that hurts or may decide to absolutely refuse to bear weight on that leg or may even sit down or lie down.
If the dog cannot put weight on the leg even when forced in the way described above, then there are chances the dog may be suffering from a fracture, an infection from some bite wound, a torn knee ligament, an unstable kneecap or even a bone tumor, explains veterinarian Dr. K.
A Closer Insight
As seen, the causes of dogs not putting weight on their back leg can be various. Sometimes the cause can be quite evident such as something stuck on the bottom of the paw, an insect bite or an infected wound, other times there may be need for veterinary investigation. Of course, the only way to know for sure is by taking the dog to the vet for proper diagnosis. Following is some more information on some possible causes of dogs not bearing weight on a back leg.
Dog Knee Ligament Injury
The dog's knee ligament in question is known as the "cranial cruciate ligament." The main task of this ligament is to stabilize the dog's knee, so when it ends up being stretched or torn, it causes pain and limping, as the knee joint becomes unstable.
A common cause for this type of injury is the dog being in motion while the back leg is held still as it may happen when the leg is temporarily stuck in a hole or somehow gets caught on a string. Affected dogs will therefore suddenly start limping on the affected leg.
One of the most common signs suggesting a torn knee ligament in dogs is what's known as "toe touching." Basically, the dog keeps the back leg mostly off the floor with only the tip of the toes making contact with the ground. This posture is mostly noticed when the dog is standing such as when eating or drinking. Also, when the dog sits, the dog may hold the leg stretched out to the side (sloppy sit) because it's painful to bend it to sit more squarely.
Dog Broken Bone
Sometimes, a dog may not be putting weight on a back leg because the bones of the foot got somehow fractured. This symptom, along with pain when manipulating the paw, is often seen when a dog has a fractured toe.
How does this happen? It may happen that the dog accidentally got his toes jammed between the planks of a deck, under a crate's door or under a regular door in the home. When the dog pulls away, the twisting motion of the paw may cause a toe fracture to occur.
Affected dogs may refuse to put any weight on the affected paw, may show signs of pain when the paw is manipulated and there may be visible swelling.
Dog Dislocated Hip
It takes some sort of traumatic injury to cause a dog to dislocate his hip, but it can happen. When a dog's hip is dislocated, the head of the femur moves out of the acetabulum, which is the socket of the pelvis. At a closer insight, what really happens is that the ligament that keeps the head of the femur within the acetabulum, ruptures, pulling away from its attachment.
Dogs affected by a dislocated hip will be unable to bear weight on the rear leg and there may be popping or crackling noises produced by movement.
Dog Unstable Kneecap
This condition is often seen in small dog breeds, and the instability leads to what's known as a "luxating patella." What happens in this case is that the kneecap pops out of place. This is something that cannot be observed with the naked eye, but that the vet can notice by palpating it.
Affected dogs may be running and then suddenly will lift the affected rear leg up and the dog may have an alarmed look on his face. Luxating patellas in small dogs can be a hereditary condition or it may occur secondary to some type of trauma.
Dog Bone Cancer
Cancer of the long bones of the dog's leg may cause severe pain and therefore reluctance to bear weight. Bone cancer is quite common in larger dog breeds and is often seen in older dogs. The pain dogs experience is due to the cancer eating up the bone. Left untreated, the bone weakens, and at some point it may fracture, what's known in medical terms as a "pathological fracture."
Because of the possibility of bone cancer, vets like to take x-rays of the affected leg's bones so to rule out this possibility. Bone cancer requires immediate intervention because it is very painful and it quickly spreads to the dog's lungs.
At the Vet's Office
If your dog cannot put weight on a back leg, see your vet as soon as possible. Your vet will ask you several questions such as when did the limping start? Did you witness any traumatic injuries? Did the limping start suddenly or did it get progressively worse?
Your vet will palpate your dog's leg and look for any swelling or signs of injury. He or she may extend and flex the leg and and look for any signs of stiffness and pain.
A drawer test may be done if the vet suspects a torn knee ligament; however, if the dog's muscles are tense, this may be inconclusive as tight muscles may temporarily stabilize the joint. The best option to rule out a torn knee ligament is to have the dog sedated during the test. With the muscles relaxed, the vet can perform a more accurate drawer's test.
X-rays for dogs who cannot bear weight can reveal signs of fractures, bone spurs or other changes associated with arthritis or signs that are indicative of the presence of cancer of the bone (canine osteosarcoma). In order to best evaluate the leg, it must be X-rayed from the tip of the toes all the way up to the hip joint. The vet may give the dog a pain killer so to be able to move the leg, therefore allowing proper positioning for the x-ray without hurting him.
Treatment depends on the underlying cause. As seen, common causes may be a torn knee ligament, an unstable kneecap or even a bone tumor, but there may be several others such as a quite severe muscle strain or sprain. If your dog cannot put weight on his back leg, therefore see your vet as soon as possible for proper diagnosis and treatment.