Identification

• The dog's knee has two ligaments that cross each other, located deep within the joint. The one toward the front of the leg is known as the anterior cruciate, whereas the one crossing behind it is known as posterior cruciate.
  
  

Function

• The main function of these two ligaments is to keep the ends of the femur and tibia from sliding back and forth across each other. Injuries affecting these ligaments are quite common, with the anterior cruciate ligament (ACL) known to be the most likely to cause problems.
  
  

Causes

• Dogs may tear their cruciate ligament in several ways.dog image by NataV from Fotolia.com
  
  Injuries to the anterior cruciate ligament may occur when the dog accidentally twists on his posterior leg. This twisting may take place when the dog falls on a slippery surface, turns suddenly when running or gets hit by a car.
  
  

Effects

• The anterior cruciate ligament may therefore eventually tear and rupture, causing the femur and tibia to no longer stay in place. Dogs affected by a ruptured anterior cruciate ligament will become lame, keep the affected leg lifted off the ground and the knee may appear swollen.
  
  

Treatment

• ACL ruptures are treated surgically.laparoscopic surgery image by Grzegorz Kwolek from Fotolia.com
  
  A ruptured cruciate ligament is treated surgically. Left untreated, most dogs will eventually develop severe arthritis. Some may also rupture the anterior cruciate of the other leg by overcompensating for the injured leg and putting more weight on the unaffected leg.
  
  

Predisposition

• The Rottweiler breed is prone to ACL injuries.Rottweiler image by Stana from Fotolia.com
  
  Obese dogs are more likely to develop injuries to the cruciate ligaments. Some dog breeds such as the Newfoundland, Labrador Retriever, Rottweiler, Bichon Frise and St. Bernard are also more predisposed than others to develop these injuries.