Cranial cruciate ligament rupture (torn knee ligament)

You may have heard of cranial cruciate ligament rupture before, as it’s a common injury  of professional footballers! In humans, this ligament is called the anterior cruciate ligament.  Injury to this ligament is surprisingly common in dogs too. In fact, it’s the most common cause of hind leg lameness in the dog

There are 2 cruciate ligaments, the cranial and the caudal in each knee joint. These are large ligaments that join the bones above and below the knee, effectively holding the knee together. The word “cruciate” just means “shaped like a cross”, as these ligaments cross over each other within the joint.

Cruciate ligament injury in humans almost always occurs as a result of excessive force on the ligament that occurs during athletic events or other such activity. While there are a number of minor factors (age, obesity, robust activity, etc) that may contribute to cranial cruciate ligament disease in dogs, the ligament almost always ruptures as part of a chronic degenerative process.

Sometimes the ligament suddenly completely 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. Often the ligaments tear only slightly to start with, and, as the tear is only partial, your dog can still weight bear and their lameness may be more subtle at this initial stage.

Your veterinarian 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 or thickened by scar tissue since this is often a chronic condition) and gently pulling on the ligaments to see if they are damaged. Sometimes it will be necessary to give your dog a sedative to examine the knee properly. Your veterinarian may want to take some X-rays of the knee to see if there has been any other damage to the joint, another cause for the lameness, or signs of disease in the other knee.

Your dog will need pain relief straight away, as this is a painful injury. While strict cage rest for 6-8 weeks may allow some smaller dogs to develop enough scar tissue to stabilise the joint; most dogs, large and small, do much better with surgery. While there are many types of surgery that have been tried, the TPLO (Tibial Plateau Levelling Osteotomy) has been shown to offer the best outcomes.

During the surgery, the torn cruciate ligament will be removed, the menisci (C-shaped cartilage pads in the knee that are often also damaged) inspected and damaged portions removed, and the TPLO surgery then performed. The TPLO involves cutting the shin bone right below the knee, rotating the cut part and fixing it with a bone plate and screws. This stabilizes the knee without the need for a cruciate ligament. Your vet will advise the best treatment option for your dog.

Post-operative care will vary depending on the type of surgery performed, but either way, your dog will often be able to come home the same day that they have the operation. They will come home with pain relief to keep them comfortable. Your veterinary surgeon will go through the post-operative care with you before your dog has the surgery. It’s important to think carefully about how you will manage this time, as your dog will need strict rest, assistance going to the loo and possibly physiotherapy. Post-op X-rays and a check to see how the surgery incision is healing will also be required.

Providing there are no other problems or complications with the joint then the operation is usually a great success for most dogs. Provided you are able to follow the post-operative instructions that your veterinarian gives you and keep your dog’s exercise restricted, they should be able to use the leg again without restriction after a couple of months (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.