Cruciate Disease in Dogs
Cruciate disease refers to partial or complete rupture of the cranial cruciate ligament. This ligament attaches the femur (thigh bone) to the tibia (shin bone) inside the stifle (knee joint). It helps hold the two bones in relation to each other during standing and walking. If the cranial cruciate ligament is damaged the femur slide backwards in relation to the tibia during weight-bearing, which is uncomfortable.
In humans, rupture of the cruciate ligament is almost always a traumatic injury. In dogs, it is generally a chronic degenerative process. In young, active dogs, the ligament may appear to “pop” suddenly (such as while running around), but it is likely there was already an underlying weakness present.
The primary symptom of cruciate rupture is limping on the affected hind leg. In most patients, this limp appears suddenly, and is such that the leg is not used at all.
As cruciate disease is usually a degenerative process, sometimes the ligament becomes gradually weaker, which may be seen as an intermittent limp or stiffness. If this happens over a long period of time, scar tissue develops which tries to support the joint. When the ligament finally ruptures, we may see that the lameness worsens but the leg is still used. In these cases, there is often muscle loss in the affected limb, meaning the thigh looks thinner than on the opposite side.
Often, we have a high index of suspicion of cruciate disease due to the dog’s breed, age and history. The key finding to confirm a diagnosis of cranial cruciate ligament rupture is instability of the stifle (knee joint). In some dogs, this may be felt while they are awake, however, most patients counteract the instability by tensing their muscles, so a definitive diagnosis is made under anaesthesia.
X-rays are also an important part of diagnosis. Some changes are seen typically with cruciate disease, which help confirm diagnosis. Cruciate disease predisposes to arthritis development which can be assessed on x-ray. Many dogs who have cruciate disease also have some degree of hip disease (hip dysplasia). This does not necessarily alter the treatment plan but can affect prognosis, so it is important to know about at the time of diagnosis.
Extra-capsular stabilisation
These techniques use prosthetic ligaments to mimic the function of the cruciate ligament and stabilise the joint. The most common is a lateral suture (involving a suture being placed around the outside, or lateral, aspect of the joint) however other techniques are available.
Extra-capsular techniques are generally simpler to perform, less expensive, with fewer risks. They are not as strong however, so are usually recommended for smaller patients, or those who do not lead a very active lifestyle.
Tibial plateau levelling procedures
These techniques aim to correct the instability by changing the biomechanics of the joint. There are several different procedures available which all work to achieve roughly the same thing. They all involve cutting bone and inserting metal implants to hold the pieces in a different position. Examples of tibial plateau levelling procedures are TPLO, TTA and TTO.
These procedures are more invasive than extra-capsular repairs and are significantly more complicated for the surgeon. For this reason, your vet may suggest that your pet goes to see a specialist orthopaedic surgeon to have one of these procedures performed. They are generally considered to give a more robust repair with better long-term outcomes, so are often recommended for very large, young or active patients.
There are few studies that objectively assess outcomes of cruciate surgery; however, one study has demonstrated that dogs who had a TPLO procedure were measured to be weight-bearing more at fixed points post-operatively when compared to patients who had a lateral suture.
