This is also a very common injury in dogs. The anatomy of your dog’s knee is very similar to people’s and has two ligaments, the anterior and the posterior cruciate ligaments. These crisscross between the femur and the tibia and keep the joint stable by preventing a forward and backward sliding motion. When one or both of these ligaments ruptures, it is extremely painful to put weight on the leg because the knee is unstable.

Athletes and athletic dogs rupture their ACL during rigorous activity, especially if the leg comes down with a twisting motion. However, the most common cause of ACL tear in a dog is obesity.

Let’s take my patient Timber as an example. Timber is a loving golden retriever who belongs to the parents of a college student. When the student went off to school, Timber's exercise routine was interrupted and he became more sedentary. However, the parents continued to feed Timber the same amount of food. Slowly he became obese. Every time the student would return home, she squawked at her parents for letting Timber get so fat, but nothing really changed, until, you guessed it, Timber tore a cruciate ligament.

Timber's surgeon took one look at him and said, “He must lose 30 pounds before I operate or this is just a waste of time! His other knee will blow in two seconds and the recovery will be brutal with all the extra weight.” We set Timber up with our in-house obesity management nurse. She calculated his necessary calories and educated Timber's owners about the amount of calories in everything he ate including human foods and treats. They had been giving him twice the number of calories that he needed. He began losing weight immediately. With pain killers, he was able to get some simple exercise so that he would be strong for his surgery..

Now, at 70 pounds, Timber is ready for his surgery and his prognosis is good.

Some dogs only have a partial ACL tear. If these dogs weigh less than 40 pounds, then they have a 70 percent  chance of recovering from the ACL tear without surgery. My sister's dog Mazzy was one of these. She had a partial tear and could bear some weight on the leg, but she also was overweight at 45 pounds. We got Mazzy on a diet as well as strong painkillers and fitted her with a specially made brace to help stabilize her knee. After six weeks of rest and weight loss she was much less painful, and at 30 pounds, she was able to walk and jog normally.

The brace that Mazzy wore is not well tested and it doesn't work for every dog. It is also rather expensive ($250) and very cumbersome. Simple knee braces, like the ones people wear, don’t work on dogs because of the exaggerated taper in the dog’s leg. Braces and bandages slide off of dog’s knees within minutes, and an improperly placed brace will do more harm than good. Mazzy’s complicated brace had straps that attach to a body harness to keep the brace from sliding down.

If this injury occurs in your dog, your veterinarian will help you determine the best plan of action. If your pet does require surgery, plan on a six-week recovery. Most surgeons require that dogs be confined to crates for at least two weeks post-operatively. Then, only restricted activity is allowed for another month.

Physical therapy is a very important part of recovery. Some exercises should be prescribed for you to perform at home. An animal rehabilitation facility can provide more sophisticated techniques. Dogs that receive physical therapy have a greater range of motion in their knees when recovery is complete.

Most dogs with ACL tears, whether they require surgery or not, will develop arthritis in their knee later in life. Using glucosamine, chondroitin sulfate and MSM combinations may help reduce and relieve these arthritic changes. Also, many dogs that tear one cruciate ligament will tear the other. This is probably because they bear more weight on the good leg while the other one is healing, and this stresses the ligaments in the other leg.

The most important thing you can do to reduce the risk of ACL tears and to encourage recovery is keep your dog lean! If it looks like your dog is going to need surgery, begin their diet immediately so that recovery is easier and the other knee doesn’t have to carry so much weight. If your pet seems to need help to lose weight, see your veterinarian. It may make the difference between a life with chronic knee pain and one without.

Dr. Katherine A. Saenger, DVM, owns Bees Ferry Veterinary Hospital and Boarding Kennel (www.beesferry.com) and is a former board member of the Charleston Animal Society (formerly John Ancrum SPCA.) If you have questions about pet behavior or health, or suggestions for column topics, e-mail her at vetsaenger@bellsouth.net, and watch the column in coming weeks for her responses. See more columns at www.moultrienews.com.