Anatomically speaking, a torn ACL in dogs is the same condition in humans, which happens when the anterior cruciate ligament of the knee suffers a loss of its integrity. In dogs, this condition is referred to as a cranial cruciate ligament tear (CCL) tear or, more generally, as cruciate ligament disease, explains the American College of Veterinary Surgeons. While many treatment options are available, the tibial-plateau-leveling osteotomy (TPLO) surgery is the most common approach to treating this condition.

Comparing Dog CCL Tears to Human ACL Tears (& Why They Happen)

While a torn ACL in humans is largely a result of traumatic events, a torn CCL in dogs is more likely to happen as a result of a progressive weakening of the ligament. As the ligament degenerates, small tears can occur, eventually leading the ligament to rupture and causing instability in the joint and an inability to successfully bear weight.

With each progressive tear, the joint becomes more inflamed. This process ultimately results in osteoarthritis.

Signs of a Torn CCL

A torn CCL in dogs may seem to come on suddenly, but in most cases the ligament has been weakening for months. Once limping is observed, pet parents tend to notice a pattern of chronic intermittent lameness lasting for 48 to 72 hours. The limping can be severe or mild.

Here are additional signs that your dog might have a torn CCL:

• Mild to severe weakening of the thigh muscles in the affected limb
• Thickening of the bony part of the affected knee
• A decreased range of motion in the affected knee
• An asymmetric sitting posture in which the lower part of the limb is angled away from the body

Some of these signs can be very subtle to nonexistent. Overt pain is not a common sign of a torn CCL. While the knee may be uncomfortable to move, lameness may be due to instability rather than discomfort.

Risk Factors

While it's impossible to know whether any individual dog will grow up to tear their CCL, some dogs are more likely to suffer CCL disease than others. Affected dogs are typically middle-aged and hail from larger breeds. According to research published in the journal Acta Veterinaria Brno, breeds at a higher risk of tearing their CCL include Labrador retrievers, Rottweilers, American cocker spaniels, chow chows, German shorthaired pointers, American Staffordshire terriers and Brazilian mastiffs. Some research indicates that this is one of the few conditions that may be more prevalent among mixed-breed dogs.

Interestingly, dogs who are neutered or spayed are more likely to experience a torn cruciate ligament. Additionally, females appear slightly more predisposed to the condition than males. Excess weight is also a risk factor.

Diagnosis & Treatment for CCL Injuries

Vets diagnose a torn CCL through physical examination, joint manipulation and X-rays. In most cases, dogs must be sedated for the exam and radiography to take place.

While TPLO surgery is the most common recommendation for a dog with a torn CCL, there are other surgical options, including:

• Simitri Stable in Stride
• Tibial tuberosity advancement (TTA)
• CORA-based leveling osteotomy (CBLO)

A great many dogs, however, will never receive surgery. Research in The Journal of Bone & Joint Surgery has shown that surgery may not even be indicated. Consequently, conservative approaches are now being more closely studied. These include:

• Weight loss
• Strict rest
• Anti-inflammatory medication
• Nutritional supplements
• Properly balanced nutrition formulated for joint health and weight loss
• Physical therapy

If a CCL rupture is diagnosed, your veterinarian will provide you with their recommendation for the best course of action, and whether surgery will be necessary or not.