Knee injuries are common in dogs, as they are in people. The most common injury in dogs is a ruptured cruciate ligament (technically the cranial cruciate ligament, as there is two. The Caudal cruciate ligament is less commonly damaged). This is called the anterior cruciate ligament in people.
These ligaments create stability in the knee. Once torn they cause pain and lameness, and unlike other tissues in the body, once damaged cannot repair themselves.
What causes cruciate injuries?
In people cruciate injury is usually caused by trauma, often during sporting endeavours. In dogs this is an uncommon cause, but may occur with dogs jumping off moving vehicles, and sudden jumping, twisting motions. ie jumping for balls and frisbees etc.
More commonly cruciate rupture is the result of a degenerative process. At this time the cause of this degeneration is unknown. However the result is that this degeneration leads to a partial tear in the cruciate ligament, causing instability in the affected joint. Osteoarthritis develops and ultimately the ligament ruptures completely.
For this reason surgery cannot avoid arthritis, as it is part of the cause of the rupture. Also dogs that rupture a cruciate ligament have a 40-50% chance of the other leg suffering the same injury.
A second injury, to the menisci can also occur in this process. The menisci are the cushions that sit between the bones, and can tear when the cruciate ruptures. This increases the pain of the injury (this is often what people mean when they refer to a torn cartilage).
Clinical signs vary between individuals depending on:
Prior to rupture an intermittent lameness, usually after exercise, may be noted. When the cruciate ruptures you will generally see a marked increase in pain, with the affected leg not being used at all.
Diagnosis of a ruptured cranial cruciate ligament is done initially buy palpation of the knee and radiographs. Most dogs with a ruptured cranial cruciate ligament will have what is called a “cranial drawsign” and “tibial thrust” on palpation . Instability of the knee is often palpable, as is thickening around the affected joint. If the meniscus is damaged a ‘click’ may also be noted. This is felt rather than heard.
The diagnosis is generally confirmed under sedation, at which times x-rays are usually taken to make sure no underlying disease process is present.
Occasionally in dogs with a chronic or partial tear of the cranial cruciate ligament (or in very tense dogs), the cranial drawsign may not be detected. In these cases, radiology is generally very useful, and may include osteoarthritis and generally joint effusion (swelling).
Sedentary dogs under 10kg body-weight, with partial or incomplete cruciate tears, may recover with strict rest and medical management, in 6-8 weeks. All other patients generally require surgery.
Surgery involves initial exploration and cleaning of the joint. The damaged ligament will be removed, and damaged sections of the meniscus taken out.
The joint is then stabilised using one of a number of techniques.
The latter techniques are often preferred for larger dogs. All of these procedures have advantages, and associated problems. We will discuss the best option for your pet with you.
Caring for your pet after surgery is generally straight forward, but crucial. Exercise should be strictly limited for the first 6-8 weeks after surgery. For some active dogs cage rest may be required. During this time some physiotherapy can be helpful.
After the first month a gradual return to exercise is appropriate. Specific forms of exercise such as swimming can be of great benefit. We will design an after care program for your dog, with you.
Your pet should be back to normal function after 3 months.
As mentioned previously arthritis is an integral part of this disease. For that reason it is common to instigate treatments for arthritis after the surgery. We may recommend any or all of the following:
Overweight dogs are more likely to rupture a cruciate ligament, and will not respond as well to surgery. Weight loss is a crucial part of recovery from this disease, for overweight dogs. We can help you formulate a weight loss program for you pet.
How do I stop this happening in my other dog?
Put simply you can’t. It is part of an inflammatory disease for which we don’t know the cause. Having said that the following tips will help if not decrease the incidence of disease, at least aid recovery from it.