Cranial cruciate ligament rupture
Cranial cruciate ligament (CCL) rupture is one of the most common causes of hind leg lameness in dogs. Several factors (breed, weight, condition) contribute to the rupture of the ACL, but the main cause is bone deformity. In the presence of an irregular articular surface, the ACL is subjected to higher loads, which leads to its degeneration and rupture.
When this ligament breaks, the only effective treatment is surgery, which is essentially to stabilise the joint. This can be achieved by implanting an artificial ligament, but in the presence of bone deformity this is not the most appropriate method.
Our clinic (the first in Lithuania) offers one of the most effective treatments for ACL rupture. We use the tibial articular surface rotation (TPLO) method. This method corrects the bone deformity and stabilises the joint. In the video below, you will see how the preparation and the surgery progress.
What is ACR?
The knee joint is stabilised by 4 main ligaments (Figure 1). The collateral ligaments are located on the sides of the knee joint and hold the bones so that they don’t ‘slide’ sideways as the animal walks, while the cruciate ligaments are located inside the joint and keep the bones from ‘moving’ forwards and backwards.
The articular surface of the tibia in most animals is sloping (Fig. 2).
The slope of the articular surface of the tibia makes the femur prone to slide downwards on this surface, as almost all joints are subject to a single main force, which is directed from top to bottom, as the animal moves. It is the ACL that ensures that the articular surface of the femur does not slide ‘backwards’ or ‘downwards’ and therefore plays a key role in stabilising the knee joint and bears the greatest load compared to the other ligaments in the knee (Fig. 3).
Why does the CCR break down?
There is no precise and concrete answer to this question. The main reason why the ligament breaks is load-related. What does this mean? When an active dog is started outdoors, it runs at full speed, spins laps without stopping, quickly changes its running trajectory or is subjected to other physical challenges in competitions. In these situations, the KKR is subjected to a much higher load than normal. The weight of the dog is also a major factor. If the dog is overweight, the force exerted on the ACL is much greater than the ligament can support. It is thought that the animal’s genes and hormones also play a role in the occurrence of the disease. Labrador, Rottweiler, West Highland White Terrier and Boxer breeds have been observed to be more prone to CKD problems. In addition to all these factors, it is very important to mention that the load on the ACL is also increased by the slope of the articular surface of the tibia. This characteristic predisposes the ACL to damage and is the main cause of degeneration of this ligament. The greater the inclination, the greater the load on the ACL (Figure 4).
In dogs with high levels of exertion, the ligament often breaks when the leg is placed in an unusual way. However, these cases should be called exceptions. It is more common for the ACL to degenerate (for the reasons already mentioned), for its fibres to weaken and for osteoarthritis to develop, with the result that the ligament breaks even without the need to exert a significant amount of force.
How do I know when my ACL is torn?
When this ligament breaks, the knee loses its stability and the femur starts to move back and forth.
The limp usually occurs suddenly and its symptoms do not get worse. Even with pain medication, animals continue to limp, avoid putting their leg up, and usually keep it raised or just touch the ground with their toes, keeping all their weight on their good leg. If the process is chronic, the animals rely on the leg but take shorter steps.
Treatment
In case of complete or partial rupture of the ACL, only surgical treatment is effective. There are many different techniques to deal with this problem. The most common worldwide is the TPLO technique (tibial articular surface rotation). The idea is to rotate the inclined surface of the tibia so that the femur does not slide. This procedure removes the cause of the load on the ACL, so the tibial plateau angle (TPA) is measured preoperatively and should be 5 degrees (+/- 3 degrees) postoperatively. The articular surface is cut, rotated to the correct angle and fixed with a special orthopaedic plate (Fig. 5), which is usually retained for life. The TPLO is practically suitable for all cases except for animals whose tibia is not inclined.
The other method is lateral artificial ligament implantation. This artificial ligament stabilises the joint, but the tibial inclination and load do not disappear, so there is still a risk that over time it will also break or develop osteoarthritis.