Anterior Cruciate Ligament Injury

ACL (anterior cruciate ligament) injury is a common occurrence in medium and large breed dogs, but can also be seen in smaller breeds. The ACL is a very important part of the knee structure, and its main function is stabilization of the knee. When an injury occurs, the knee becomes unstable and therefore painful. Lameness is the first symptom that owners notice, and this is generally worse after exercise, and is also very noticeable after the dog has been sleeping for a while. In some cases the dog seems to improve with gentle or moderate exercise, but is always uncomfortable after any strenuous activity. The ACL has two parts, and your pet may have a partially torn ligament rather than a complete tear. These cases can be a little more difficult to diagnose.

ACL injuries are painful . Dogs hide their pain and discomfort much better than we humans do. When your pet is showing evidence of discomfort (pain), you should acknowledge this and realize that help is needed. When a dog with an ACL injury is presented for a veterinary examination, they are often tense and protective of the injured area. I always recommend radiographs under deep conscious sedation. A nicely sedated pet will allow a much better examination of the affected knee. Generally, it is obvious that the injured knee has increased laxity; it is simply looser than the good knee. It is important to compare both knees, and unfortunately, it is not unusual to find that both knees are affected . I do radiographs of the injured knee in extension and flexion, the other knee for comparision, and also the hip joints. Sometimes there is evidence of hip dysplasia or osteoarthritis, and these conditions can affect the outcome and recommendations for the damaged knee.

In medium and large breed dogs, torn ligaments rarely, if ever, heal by themselves. The knee will try and adjust to the new situation and restructure itself. In chronic cases, we often see increased build up of bone on the inside of the knee. This is called a buttress and is an attempt to stabilize the knee. In dogs, the ACL is always under tension, even at rest, because unlike us they are not able to hold the leg straight; the knee is always bent. Some dogs have straighter legs than others, and these individuals actually have a higher incidence of injury.

Surgery is generally regarded as the best long term option for cruciate injuries. The aim of surgery is to maximize stability of the knee, and therefore greatly reduce the amount of arthritis that occurs. Any time a dog tears their ACL, the knee pays a penalty and that simply is arthritis. Surgery, even in cases which are done immediately, does not result in no reaction to the injury in that knee. The surgery is advised in order to keep the knee as fully functional as possible, for as long as possible. Arthritis will develop, but depending on the type and the skill of the surgeon, that level of arthritis will be infinitely less than what will develop if the knee is not treated. The difficulty for owners is deciding on what type of surgery to choose. There are many methods and not all of them give the best results. In simple terms, the surgeries can be divided into two camps; extracapsular repair, and joint reconstruction.

Extracapsular repair involves use of a synthetic material to mimic the function of the ACL, and thereby stabilize the joint. I have used this method for 30 years and the results tend to be very satisfactory in dogs under 40 lbs, good for dogs 40 to 60 lbs, and reasonably good for 60 to 90 lbs. For the bigger dogs, a lot depends on age, weight and activity levels.

The most satisfactory repair for larger dogs is joint reconstruction, and there are two methods widely used and with similar and excellent results. They are know as TTA and TPLO. In both cases the bone is cut with a special orthopaedic saw, and the knee is rearranged with specially designed plates, screws and bone cages. these two surgeries are far more advanced than extracapsular repair, and require specialized equipment and training.

The deciding factor for most people is cost, and of course, the specialized methods of repair (TTA and TPLO) are more expensive. .I have been offering the TTA method for the last two years and have done various methods of extracapsular repair for the last thirty years. The results achieved with the TTA method have generally been very good, to far better than expected. Patients recover much faster and generally are as good in one week post surgery as the extracapsular patients are in 6 weeks. The problem is that these patients seem to be very good, and doing so well that some owners feel they should be allowed the "freedom" of being off leash. It takes a minimum of 8 weeks for the bone to heal properly and even longer in older patients. Until the bone is healed fully, all the stress is put on the screws which hold the plate, and that can be too much if a pet is allowed to be off leash, twisting, turning and being exuberant. No off leash is advised or allowed until the radiographs at 8 to 10 weeks show that the bone is healed. Then the dog can be gradually conditioned to full fitness.

Please remember that all hind limb lameness does not mean that there is damage done to the ACL. Some dogs have osteoarthritis of the hip, knee or tarsal(ankle)joint. Some may have hip dysplasis and others may have a fracture or a joint dislocation. Radiographs will give the needed information to make a satisfactory diagnosis.

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