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ACL in dogs

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ACL (Anterior cruciate ligament) injuries are more common in dogs than other pets.  An ACL rupture is a knee injury in dogs, especially common in those that are very active or athletic.  The risk of ACL knee injury increases dramatically in overweight dogs.

The anterior cruciate ligaments (ACLs) are two bands of fibrous tissue found in each knee joint.  They join the bones above and below the knee joint (femur and tibia), so that the knee works like a hinge, moving only backward and forward.  The two ligaments cross each other as one travels from the front to the back of the knee joint, and the other travels from the back to the front.

An ACL is most often ruptured, or torn, when the knee joint is twisted.  This happens most often when dogs are running and then suddenly change direction.  The joint becomes unstable, causing pain and usually a non-weightbearing lameness.  If the cruciate ligament is stretched or only partially torn, it becomes weaker than normal and lameness may be less severe or intermittent.  However, with time, the ligament nearly always tears completely.

Diagnosis is based on the history and a physical examination.  The dog may have suddenly stopped or cried out when running, and then was unable to bear weight on the leg.  As part of the examination, your veterinarian will perform a specific knee manipulation, looking for what is called "drawer movement."  This movement in the knee indicates instability in the joint and is characteristic of cruciate ligament injury.  Other tests, such as x-rays or arthroscopy, may also be needed.

Surgery is almost always required to repair the damage to the cruciate ligament.  In most cases, artificial ligaments are placed along the outside of the knee to reinforce and stabilize the joint.  You will need to limit your dog's activity for 6-8 weeks after surgery, gradually returning to normal activity within 3-6 months.  Physical therapy may speed recovery and reduce complications.  Arthritis commonly develops in the joint with age.



What are the cruciate ligaments?

The cruciates are two pair of crossed ligaments (one pair in each knee) that keep the knees from sliding in and out as they bend.

How is a cruciate ligament injured?

A cruciate ligament is most often ruptured or torn when the knee joint is twisted.  This usually happens when dogs are running and then suddenly change direction.  

How can you tell if a cruciate gets damaged?
The joint becomes unstable, causing pain and usually a non-weightbearing lameness.  Your vet can check the knee for signs of the in and out “drawer movement” that is indicative of this condition.  

How do you correct cruciate injuries?
Cruciate ruptures require surgery to stabilize the joint, followed by 6-8 weeks of rest to allow the area to heal.  Over time, exercise therapy can be used to return the knee to normal function and to keep your dog fit and trim so that the problem does not recur.


Credit: Written and reviewed by John A. Bukowski, DVM, MPH, PhDand Susan E. Aiello, DVM, ELS
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