ACL Damage in a Dog

ACL (anterior cruciate ligament) damage is the number one cause of lameness in dogs today, according to veterinarians Race Foster and Marty Smith. The ACL is one of the ligaments that stabilizes the stifle (knee) joint in dogs. The ACL is most commonly damaged when a dog twists a hind leg while running on a slippery surface or when a dog is hit by a car. Surgery may be the only option to repair ACL damage.

  1. The Stifle Joint

    • The knee on a dog is called the "stifle joint." The stifle joint connects the femur, which is the long bone from the hip, to the tiba, which is the lower bone between the knee and the ankle. The third bone in the stifle joint is the patella, or the kneecap. The bones in the stifle joint are connected and stabilized by bands of tissue called ligaments. These ligaments cross over the knee, which is why they are called "cruciate" (cross) ligaments. The ligament at the front of the leg is called the "anterior cruciate" ligament (ACL) and the ligament behind is called the "posterior cruciate" ligament. The ligaments prevent the femur and tibia from moving back and forth across each other.

    Types of ACL Damage

    • The ACL can degenerate slowly over time until it becomes so weak that it ruptures without any injury. The ACL can also be damaged suddenly due to injury. The symptoms of ACL damage depend on its severity. The damage can be a partial or complete rupture of the ACL. A complete rupture manifests as sudden lameness, with the dog holding the foot off the ground and the leg in a partially bent position while standing. Dogs with ACL damage often sit awkwardly with the leg sticking out to the side.

    Diagnosing ACL Damage

    • ACL damage is diagnosed with a drawer test. A veterinarian will manipulate the stifle joint in a particular way to determine any abnormal movement. Nervous dogs may need to be sedated for the veterinarian to get accurate results from the drawer test. Researchers at the University of Wisconsin-Madison School of Veterinary Medicine have designed a piece of equipment that can assist in the early diagnosis of a stretched or torn ACL, which might prevent full rupture damage.

    Repairing ACL Damage

    • Some veterinarians recommend that dogs under 33 pounds receive outpatient treatment for ACL damage. Others recommend stabilization surgery for all dogs with ACL damage. There are several different surgeries available ranging from recreating the ligament to moving part of the tibia to changing the angle of the tibia. For any of these surgeries, dogs require four to six weeks of restricted activity recovery time.

    Alternatives to Surgery

    • While stabilization surgery speeds recovery and enhances function, some dog owners do not want to take the risk associated with surgery. The alternative to surgery primarily involves relieving pain and maintaining muscle strength to provide some stabilization. Low-impact activities like walking and swimming can help to improve muscle strength. Nonsteroidal anti-inflammatory drugs can help to relieve pain. Veterinarians also recommend supplements containing glucosamine, chondrotin and perna mussel.