Dear Dr. Thompson: My dog tore a ligament in his hind leg a couple of months ago and I went to the vet and they recommended surgery. A few sites on the Internet suggested that dogs will do OK without surgery, so I watched him and he was doing fine until he did the same thing to his other hind leg just a few weeks ago.
Now he won't eat his food and I wonder if it has anything to do with his injury. Why would he eat treats and canned food and all of the sudden not eat his regular food?
There are two issues I would like to address in your question. You did not mention whether or not your veterinarian prescribed anything for your dog, but my concern would be digestive upset from any pain medication, which is a common side effect of non-steroidal anti-inflammatories.
You should stop any medications you might be giving and have him evaluated because a mild stomach ulcer can progress to a perforation which could be a life-threatening emergency. Remember that over-the-counter medications for people can have devastating consequences in dogs, so never give anything without consulting your veterinarian first.
I am equally concerned about the information you found on the Internet. The Internet is a great source of information but a terrible source of knowledge and it applies to this situation.
The ligament tear your veterinarian diagnosed is most likely a cranial cruciate ligament, which is equivalent to an ACL in people. This ligament is a major stabilizer of the knee from front to back. With the exception of dogs under five or 10 pounds, a cruciate rupture is always a surgical problem.
There is some research in people suggesting a small percentage of patients may be able to aggressively rehabilitate ACL injuries in order to avoid surgery, but the biomechanics of the dog knee are entirely different, so it is not an apples-to-apples comparison.
People have a relatively flat weight-bearing surface in the knee and we can function without an intact ACL. However, dogs have a steep slope in the knee and without an intact cruciate ligament any weight-bearing results in instability. This buckling and movement is painful, which is why dogs limp.
I often hear that the dog isn't in pain because he does not cry out when the leg is manipulated, but think how much pain it would take for you to cry out, and simply flexing or touching the knee does not match what occurs when weight is placed on the leg.
Over time, debilitating arthritis develops in the knee from the instability. Another unfortunate side effect is that your dog was bearing most of his weight on the other leg and has gone on to blow out his other knee. Now he is bearing most of his weight on his two front legs.
There are multiple surgical options for dogs with a torn cruciate ligament and depending on your dog's size and level of activity, your veterinarian can suggest the best option.
However, without treatment he will live with two painful knees.
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