This information is provided by Provet for educational purposes only.
You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.
The cruciate ligaments are two of the main ligaments which lie in the knee (stifle) joint and help to stabilise it. There are two cruciate ligaments ...the anterior and the posterior ligaments, and these often get torn when the knee is injured.
Tearing of the cruciate ligaments is a common injury in large breeds of dog, but it can be seen in any animal.
The knee joint is complicated because it has to be able to flex and extend, but at the same time the upper and lower bones cannot be allowed to move too far apart because they are bearing a lot of weight across the joint. The cruciate ligaments help to check the forward and rotational movement between the two main bones (the upper femur and the lower tibia). If they get torn the bones can move too far apart during weight bearing and so the joint is unstable and the dog is very lame. Immediately after rupture the joint is very painful and sometimes swollen as well.
Typically the cruciates rupture during exercise ...often when the dog is weight bearing on the leg and twists the knee during turning.
Small dogs may be able get good functional use back in the joint following rest, but in larger heavier dogs surgical repair is usually needed.
Complications following a ruptured cruciate include the development of arthritis, and sometimes the repair can breakdown before the joint is stabilised.
Updated October 2013