I know that knee injuries are common in people. Do they occur in dogs?
The knee joint of a dog is one of the weakest in the body. Just as football players and skiers frequently suffer knee injuries, dogs also have knee injuries.
Why is the knee so likely to be injured?
The knee joint is relatively unstable because there is no interlocking of bones in the joint. Instead, the two main bones, the femur and tibia, are joined with several ligaments. When severe twisting of the joint occurs, the most common injury is a rupture of the anterior cruciate ligament (ACL). When it is torn, an instability occurs that allows the bones to move in an abnormal fashion in relation to each other. It is not possible to bear weight on the leg without it collapsing.
How is it diagnosed?
The most reliable means of diagnosing this injury is to move the femur and tibia in a certain way to demonstrate the instability. This movement is called a "drawer sign." It can usually be demonstrated with the dog awake. If the dog is in pain, has very strong leg muscles, or is uncooperative, it may be necessary to use sedation in order to examine the joint thoroughly.
How is it treated?
Correction of this problem requires surgery. A skilled surgeon can fashion a replacement ligament and stabilize the joint so it functions normally or near normally. If surgery is not performed within a few days to a week, arthritic changes will begin that cannot be reversed, even with surgery.
I have heard of torn cartilage. Does this also occur?
Occasionally the injury that causes a ruptured anterior cruciate ligament (ACL) will also result in tearing of one or both of the menisci or "cartilages." At the time of surgery, these are examined and removed if necessary.
What happens if surgery is not performed?
Occasionally, the dog that has a ruptured cruciate ligament will become sound (will no longer limp) even if surgery is not performed. However, arthritis will usually begin and result in lameness a few months later. That lameness cannot be corrected.
My dog is overweight. Does that relate to this injury?
A special note is appropriate concerning a dog's weight. Obesity or excessive weight can be a strong contributing factor in cruciate rupture. The ligament may become weakened due to carrying too much weight; this causes it to tear easily. Obesity will make the recovery time much longer, and it will make the other knee very susceptible to cruciate rupture. If your dog has a weight problem, there are prescription diets that can be used to assist weight reduction.
For more information on knee injuries in dogs visit https://www.acvs.org/small-animal/cranial-cruciate-ligament-disease