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Sophie, my American Staffordshire Terrier mix, was chasing down a tennis ball when she made a sharp turn and then stopped dead in her tracks. She limped back to me, holding her right hind leg aloft. Had she stepped on something? Was it a sprain?
In Sophie’s case, her injury was a complete anterior cruciate ligament (ACL) tear that required surgery. ACL tears or ruptures are one of the most common knee injuries for dogs, affecting more than one million dogs every year.
What are the Symptoms of an ACL Tear?
Like Sophie, dogs who have ruptured their anterior cruciate ligament usually appear to be suddenly lame, according to Holly Nash, DVM, MS, on peteducation.com, and hold the foot of the injured leg off the ground.
“In time, the dog may start to use the leg again, but often lameness returns,” Nash writes. “Dogs with a degenerating ACL may also show some pain, and there may be some swelling in the joint.”
What Can Cause an ACL Tear?
Your dog’s knee joint comprises three bones: the femur (a long bone extending down from the hip); tibia (the bone between the knee and ankle); and patella (kneecap). These three bones are joined together by tough bands of tissue, called ligaments.
The anterior cruciate ligament (ACL) is toward the front of your dog’s leg, and the posterior cruciate ligament (PCL) crosses behind it. Mar Vista Animal Medical Center notes that the ligaments are “holding everything together, allowing the knee to bend the way it should and keep it from bending the way it shouldn’t.”
The ACL can be torn when a dog twists on his hind leg. “The twisting motion puts too much tension on the ligament and it tears,” Nash writes. This can happen if a dog falls on a slippery surface, is hit by a car or, like Sophie, makes a sudden turn while running.
ACL tears can also occur in obese dogs, since there is extra weight on the knee. In these cases, the ACL can slowly degenerate until it ruptures, without a sudden injury. “In this type of patient, stepping down off the bed or a small jump can be all it takes to break the ligament,” writes Mar Vista. Overweight dogs that rupture the ACL in one leg frequently rupture the other one within a year, warns Mar Vista, so pet parents should be prepared for another surgery.
According to Nash and Mar Vista, the following breeds have a greater risk of ACL degeneration:
“In small-breed dogs, a luxating patella may predispose them to a ruptured anterior cruciate ligament,” Nash writes.
How is an ACL Tear Diagnosed?
According to Nash, your vet will check for abnormal movement of your dog’s knee joint by placing one hand around the femur and the other around the tibia, and then applying pressure on the knee. The abnormal movement is called a “drawer sign.”
“It is called that because the movement of the femur in relation to the tibia is similar to pulling and pushing in the drawer of a cabinet,” Nash explains. “If an animal is in a lot of pain, or very nervous, the muscles near the knee may be so tense that they prevent the drawer movement from occurring.”
Your dog’s knee will probably also be X-rayed to determine the extent of arthritis that may be present.
How is an ACL Tear Treated?
If your dog’s anterior ligament is completely torn, surgery is usually required to treat it. There currently are three common surgical procedures for repairing a torn ACL: tibial plateau leveling osteotomy (TPLO); tibial tuberosity advancement (TTA); or tightrope CCL.
Tibial plateau leveling osteotomy (TPLO) – To stabilize the joint, part of the tibia is removed and attached to a different part of the tibia using plates and screws. Nash writes that while this type of surgery (which was performed on Sophie) is technically difficult, “it has shown to produce excellent results, often with less arthritis.” It is usually recommended for dogs that weigh more than 50 pounds.
Tibial tuberosity advancement (TTA) – A portion of the tibia is cut and allowed to heal at a different angle to alter the stress placed on the joint. As with the TPLO, complicated TTA surgery is performed by vets with special equipment and training.
Tightrope CCL – This procedure was developed just two years ago. It is much less invasive than TPLO or TTA, requiring only small incisions and small holes drilled in the bone, according to the University of Missouri College of Veterinary Medicine (MU). “Other current techniques require major surgery that involve cutting the bone, which can potentially lead to severe complications, such as fracture, implant failure and damage to the joint,” said MU veterinarian James Cook, who helped develop the procedure. But it’s not for every dog. MU reports that dogs must weigh at least 40 pounds so that tunnels can successfully be drilled in their bones. After surgery, a 10- to 12-week rehabilitation period with limited activity is essential for recovery, so this surgery may not be appropriate for extremely active dogs.
Non-surgical treatment – If the ACL is only partially torn – or if you have an older dog or your dog has a medical condition that could affect recovery – Nash writes that the condition may be treated by restricting your dog’s activity for two to three months. To maintain your dog’s muscle strength, your vet may allow low-impact exercise like swimming and short walks. If your dog is overweight, you should feed him a reduced-calorie diet. Your vet may prescribe nonsteroidal anti-inflammatory drugs (NSAIDS) to reduce inflammation of the joint and relieve pain. Glucosamine and chondroitin supplements can also help repair the joint.
If your dog has a complete ACL tear that goes untreated, he will usually develop severe degenerative joint disease (arthritis). Also, because your dog will put more weight on the unaffected leg, it’s not unusual that he may tear the ACL in that leg as well due to the increased stress. Mar Vista notes that “Bone spurs called ‘osteophytes’ develop and chronic pain and loss of joint motion result. This process can be arrested by surgery but cannot be reversed.”
How Should I Treat My Dog After Surgery?
“After the surgery, the dog must be strictly confined for two weeks,” writes Nash. “By day 10 after surgery, most dogs touch the toe of the affected leg to the ground and will start bearing minimal weight on the leg. Once the dog has reached this point, it is often very difficult to keep the dog quiet until complete healing has taken place.”
For the next four to six weeks, your dog will probably be restricted to only leash walking, depending on the extent of his injury and the type of surgery. “This is extremely important to prevent the surgical correction from tearing,” Nash writes. “The veterinarian’s instructions regarding exercise during the recovery period should be followed very carefully.”
If you limit your dog’s activity after surgery, and if you see to it that your obese dog loses weight, the prognosis for a full recovery is very good.
In Sophie’s case, a few months after her TPLO surgery she was back to fully enjoying her tennis-ball-chasing activities. The only evidence she’d ever had an injury was a thin scar on her right leg.
Find A Vet HOW TO articles are intended for informational purposes only. You should always consult with your veterinarian about any health issues affecting your dog.