There are two cruciate ligaments in a dog’s knee joint. These ligaments connect the femur (thigh bone) to the tibia (shin bone) and stabilise the knee joint.
The ligament can rupture completely or partially. A ruptured cruciate is a painful injury and can prevent the dog from walking on that limb.
Signs of a cruciate ligament injury
When the cruciate ligament tears, the tibia moves forwards and backwards under the femur, causing inflammation, pain and lameness. Sudden lameness in a rear leg is often the first sign.
The lameness can worsen with activity and improve with rest. If an injury remains unaddressed, arthritic changes occur quickly. This leads to chronic lameness and discomfort. If your dog suddenly shows signs of pain or limping, they should be taken to the vet. Some muscular injuries may resolve with a week of pain relief and rest, but if the lameness has not resolved within 1 week, the dog will need to have X-Rays taken.
Causes of a cruciate ligament injury
The two main causes of cruciate ligament rupture in dogs are degeneration of the ligament and trauma.
A tear can result from an athletic injury in a healthy dog, for example, from landing badly when running or jumping. Overweight dogs are more prone to ligament injury, as they carry more weight and are prone to ligament degeneration.
Some dog breeds are predisposed to cruciate ligament injuries including rottweilers, Labrador retrievers, Newfoundlands, and Staffordshire terriers.
How to prevent a cruciate ligament injury?
While a cruciate rupture cannot always be prevented, keeping your dog at a healthy weight and providing plenty of gentle exercise can minimize the risk.
How to treat a cruciate ligament injury?
Medical management (rest and anti-inflammatories) is possible for smaller dogs (<10kg) to recover but it is very unlikely that dogs over >10kg will recover without long term pain. Medical therapy involves several weeks of cage rest, with brief, calm leash walks for bathroom breaks only. Dogs will also be on long term anti-inflammatory drugs and supplements to support joint health. These dogs will develop osteoarthritis in the affected knee joint.
Although rest and medication may help, surgery is recommended to repair the ruptured cruciate ligament. All knee surgeries at Matraville Veterinary Hospital are performed by an external orthopaedic specialist surgeon. Some general practitioners perform this surgery and may be cheaper than a specialist however we always recommend that a specialist performs cruciate surgery, as their training and experience is much more advanced, resulting in much less risk of complications.
In general, prognosis after surgery is excellent, with most dogs returning to normal activity level.
Types of cruciate surgeries
In this method, a strong suture is placed to secure the femur and tibia together, essentially replacing the function of the torn cruciate ligament. The suture supports the knee joint while scar tissue builds up around the joint and the muscles surrounding the joint strengthen.
This is a relatively quick and uncomplicated procedure with good success rates in smaller dogs. It is less expensive than other methods. Success is less likely in heavier dogs. This technique is not recommended for dogs >20kg and success is variable in dogs between 10-20kg depending on the dogs activity level.
Another surgical option is the tibial plateau leveling osteotomy (TPLO). This is a more complex procedure than the extracapsular method and requires specific surgical equipment and training.
The TPLO alters the biomechanics of the knee joint, allowing it to function properly without a cruciate ligament. A complete cut is made through the top of the tibia (tibial plateau). The tibial plateau is rotated to change the angle of this portion of the bone. A metal plate is affixed to hold the cut bones in place while they heal over the following months.
Generally, the long-term prognosis is good, and re-injury is uncommon. The plate does not need to be removed unless problems occur later.
As with any surgery, complications are possible, including infection. Patients go home with antibiotics to prevent the possibility of infection.
Cruciate surgery recovery
Regardless of the type of surgery, the post-operate period is extremely important after a cruciate surgery.
Strict rest is required for the 8 weeks following surgery. This is because of 2 reasons:
- To allow optimal healing of the surgical site,
- To prevent excess strain on the opposite leg – which will be predominantly weight bearing during the post-op period.
Dogs have a 40 to 50 percent chance of tearing the ligament in their other knee. If the opposite leg is prone to too much weight bearing, it will put the cruciate ligament of that leg at risk of the same injury.
The best way to keep your dog quiet after the surgery is to keep him/her confined to either a small room or a playpen.
Following your vet’s recommendations will give your dog the best chance of full recovery with fewer complications. As with any orthopedic surgery, it is common for dogs to develop arthritis in the future. With proper care, your dog can live a full, healthy, and comfortable life.