Cruciate injuries - what are they and how do we treat them?
Cruciate injuries are probably the most common hindlimb lameness in the dog we see in small animal practice. It can occur in cats, but much less frequently.
What and where are the cruciate ligaments?
The word cruciate means 'to cross over' or 'form a cross'. In the knee two cruciate ligaments are found. Simplistically these are strong elastic bands that join the thigh bone (femur) and shin (tibia) so that the knee works as a stable hinge joint.
One ligament runs from the inside to the outside of the knee joint and the other from the outside to the inside, crossing over each other in the middle. You may be familiar with the human term anterior cruciate rupture, in dogs the same ligament is often prone to damage but we call it the cranial cruciate ligament.
How does a cranial cruciate injury occur?
Anatomically the knee joint is a hinge joint. Unlike the hip joint, no bones interlock, this makes it relatively unstable. Instead it is held together by several strong ligaments, including the cruciate ligaments, which allow it to move back and forth like a hinge, but restrict its side-to-side motion.
The two most common causes of cranial cruciate rupture in the dog are trauma and degeneration of the ligaments within the joint.
- Traumatic cruciate rupture is caused by a twisting injury to the knee joint. This occurs most often when the dog is running and suddenly changes direction. This injury usually affects the cranial (front) ligament. A cruciate ligament rupture is usually extremely painful and the knee joint becomes unstable, resulting in a severe and sudden lameness.
- A more chronic but not uncommon form of cruciate damage in the dog occurs due to progressive weakening of the ligaments. Initially, the ligament becomes stretched or partially torn over time, lameness being only slight and intermittent. With continued use of the joint, the condition gradually gets worse until a complete rupture occurs.
Are certain dogs more likely to suffer this type of injury?
Certain breeds are more prone - larger deep chested breeds such as the Labradors and Rotties are amongst some. Bichons tend to be one of the more prone of the smaller breeds
Obese dogs appear to be more predisposed to develop cruciate rupture. Those with other knee problems may also be predisposed to rupturing their cruciate ligaments.
Unfortunately dogs who rupture one cranial ligament are more predisposed to rupturing the cranial cruciate ligament in the other knee.
How is it diagnosed?
With traumatic cruciate rupture, the usual history is that the dog was running and suddenly stopped or cried out and was then unable to bear weight on the affected leg. Many pets will 'toe touch' and place only a small amount of weight on the injured leg.
Diagnosis can be a combination of specific manipulations of the limb while conscious but often needs further examination under sedation and x-rays are often necessary to help confirm the diagnosis.
Is an operation always necessary?
Dogs weighing less than 10 kg may heal without surgery, provided they have severe exercise restriction such as strict cage rest for at least 6 to 8 weeks. However dogs over 10 kg usually require surgery to stabilise the knee. Hydrotherapy and physiotherapy can be extremely useful in aiding recovery in these cases and should be considered. Unfortunately, most larger dogs will often require surgery to correct this painful injury.
What does surgery involve?
There are a multitude of surgical techniques performed to stabilise the knee joint following cruciate rupture. The joint is inspected and fragments of torn ligament and cartilage are removed. Surgical stabilisation is then carried out. Broadly speaking one of two techniques is used. Extracapsular repair, where an artificial ligament is used to support the joint out side of the joint capsule and Intracapsular repair, where the anatomical alignment of the joint is corrected using a combination of bone cutting and plating.
Each carry their own advantages and disadvantages. At Stone Court Vets we are able to offer both a extracapsular (lateral suture) and an intracapsular, (TTAR) option. We will discuss the options with you and whether we think hydrotherapy and/or physiotherapy should also be recommended.
Unfortunately, regardless of the technique used and particularly if conservative treatment is used, arthritis is likely to develop in the joint as your dog ages. Weight control and nutritional supplements may help delay the onset of arthritis in your pet which we will advise you on.