Part I: Symptoms and Diagonosis | Part II: Treatment and Management
Anterior Cruciate Ligament (ACL) injuries are one of the most common orthopedic injuries veterinarians see in dogs. The ligament is also known as the Cranial Cruciate Ligament (CCL) in animals. It connects the bone above the knee (the femur) with the bone below the knee (the tibia). Essentially, the ACL stabilizes the knee (or stifle) joint.
Canine stifle or knee joint
It does not matter the size, breed, sex or age of the dog, all dogs can get an ACL injury. That said, studies have shows certain breeds are more prone to ACL injuries. These include: Labrador Retrievers, Poodles, Golden Retrievers, Bichon Frises, German Shepherd Dogs, and Rottweilers.
Other predispositions to ACL injury include:
An ACL injury is extremely painful and affected dogs experience pain while simply walking. A tear or rupture leads to joint swelling, pain and instability in the knee joint. If left untreated it will cause lameness in the affected rear leg and, ultimately, chronic irreversible degenerative joint changes. Damage to the ACL is a major cause of progressive osteoarthritis in the knee joint of dogs.
The good news is that there is a high success rate with surgeries performed to repair ACL injuries and that dogs who receive surgical treatment can resume regular activities after rehabilitation.
ACL injuries can be caused by many factors, although the exact reasons as to why it is so common in dogs is not completely understood. Continual biomechanical wear and tear eventually causes the ACL to break down until it reaches a point that the ligament tears completely. Simple activities such as walking, running and jumping, all cause wear and tear. Obesity, traumatic injuries or strenuous or repetitive activities can also cause the ACL to deteriorate.
ACL injuries in dogs do not always occur during athletic activities. Some dogs will be making a simple movement like jumping off a couch or going down a stair when their ACL will tear or rupture.
Most acute (sudden) ACL injuries in dogs occur during strenuous or exuberant activities, such as playing, chasing, roughhousing, running, hunting, jumping or engaging in other "doggie" fun. Sometimes a dog will simply stumble and when they get up they will have ruptured their ACL. Other times ACL injuries will develop slowly over time. This can be caused by genetic abnormalities that cause poor muscle tone or poor neuromuscular coordination. Obesity also contributes to chronic ligament damage because of the extra weight placed on the joints.
There is no straightforward way to prevent ACL injuries in dogs. Keeping your dog healthy and in good physical condition is the best prevention, but by no means guarantees your dog will avoid tearing their ACL.
Well-conditioned dogs are better able to avoid injuries, because their joints and bones are protected from outside stressors by strong surrounding musculature. General rules of thumb are:
Often symptoms of ACL injuries are gradual and a dog will slowly become more lame as the ligament becomes more damaged. Other times, when there is a rupture or tear, there is no advanced warning signs. Nearly all dogs with tearing or damage to their cruciate ligament will have swelling that is felt on the front part of their knee.
Symptoms may include:
Veterinarians use a test called the cranial drawer test to check the cranial cruciate ligament for looseness. The test is called a drawer test because the movement of the femur in relation to the tibia is similar to pulling and pushing in the drawer of a cabinet. The affected knee is tested for palpable laxity or looseness, which is referred to as cranial drawer instability.
A drawer movement in the knee accompanies a ruptured ACL.
Secondarily, a radiograph (X-ray) will be taken to determine the extent of the ACL damage and the progression of the injury. X-rays also will likely reveal if there is any fluid or arthritis in the joint or if there are bone spurs or fragments.
Partial ruptures are more difficult to diagnose. Dogs with partial ligament tears will usually have swelling of their knee and pain when their knee is completely extended.
The video below summarizes symptoms and diagnosis of ACL injuries.
Next - Part II: ACL Injuries in Dogs: Treatment and Management
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