Cruciate ligament rupture is the famous knee injury of professional footballers. It is surprisingly common in dogs too. If the ligaments are damaged they need to be replaced during an operation on the knee. After the operation most dogs return to full athletic fitness.
The ligaments are damaged by a twisting injury to the knee. This is most often seen in athletic dogs who jump or turn suddenly while running. Some breeds seem to have weak ligaments and the ligaments in all dogs get weaker with age and so tear more easily. Damage can also happen in obese dogs due to the excess strain on the joints.
Sometimes the ligament suddenly tears. If this happens it is most likely to occur when your dog is running around at exercise. They will pull up, hopping lame on one back leg. Dogs with cruciate ligament tears stand in a very characteristic way with their back toe just touching on the ground but not taking any weight on the affected leg. Often the ligaments tear slightly to start with and this may make your dog lame on and off for a while.
Your vet will probably suspect what is wrong with your dog from your description of the symptoms. They can confirm what is wrong by feeling the knee joint (which will probably be swollen) and pulling on the ligaments to see if they are damaged. Sometimes it will be necessary to give your dog an anaesthetic to examine the knee properly. Your vet may want to take some x-rays of the knee to see if there has been any other damage to the joint or signs of disease in the other knee.
Just as in humans, the damaged ligaments can be replaced by a man-made tape. This requires an operation on the knee joint. In some very small dogs, if the damage to the ligament is not too severe, the knee may recover if you rest your dog for a few months. In larger dogs the knee will never recover until the surgery is performed. Even in those dogs who only have a partial tear in the ligament, surgery is the best option. These dogs may get better with rest but are prone to injuring the ligament again as soon as they are allowed to return to normal exercise. Some large dogs may benefit from a special operation called tibial plateau levelling. This may give better results than conventional surgery but is only available at a few specialist centres.
The operation is relatively straightforward and often your dog will be able to come home the same day that they have the operation. In some cases your vet may decide to refer your pet to a specialist for surgery and in this case your dog may need to stay in the hospital for a day or two. For the first week after the operation your dog might have to wear a large support bandage to stop them bending the leg. This bandage will have to be checked by your vet every couple of days to make sure it is not rubbing on the leg. The large bandage will be removed at about the time the stitches come out. Your dog should be confined to a small area of the house and will need to be exercised on a lead only for 6-8 weeks after the surgery.
The operation is usually a great success in most dogs. Provided you are able to follow the post-operative instructions that your vet gives you and keep your dog’s exercise restricted, they should be able to walk on the leg again after a few weeks (although it may take many months before they are using the leg normally and it is as strong as it was before the operation). As your dog gets older they may develop some stiffness in the joint – it is quite usual for arthritis to develop in a joint that has been operated on.