Cruciate Ligament Injuries in Dogs

Rupture

• The cruciate ligaments keep the femur and tibia from rubbing against each other. The rear ligament is called the posterior cruciate ligament, and the front ligament is the anterior cruciate ligament. The cruciate ligaments are likely to rupture (tear) during twisting motions. If the dog overextends his knee, the ligaments will tear away from the bones, allowing the femur and tibia to rub against each other.

Risks

• Dogs most at risk for cruciate ligament injuries are those who are extremely active. Larger breeds, particularly labs, rottweilers and St. Bernards, are also at risk. Obese dogs of any size have an increased incidence of ruptured cruciate ligaments. The excess weight puts more pressure on the ligaments, wearing them thin over time. Cruciate ligament injuries in obese dogs are more likely to happen gradually instead of through physical activity or injury. Dogs hit by cars often have cruciate ligament injuries, too.

Signs

• Dogs usually display lameness. In a sudden injury, he will show signs of pain immediately, often favoring the injured paw. He might cry when trying to bear weight on the sore knee. The knee joint will often appear swollen and might be warm to the touch. For dogs with progressive degeneration of the cruciate ligaments, you will often notice a tendency to favor a paw for a few days before you dog starts walking on it again. This cycle tends to repeat. Her knee might appear swollen during times when she is favoring it, and even when she isn't.

Diagnosis

• If your vet suspects a ruptured cruciate ligament, she will perform a physical exam. In a precise manner, she will manipulate the femur and tibia to see if they bones are moving abnormally. If your dog is too nervous or in too much pain to tolerate an exam, your vet might sedate him first. She might also order X-rays to determine the extent of the injury and to check for arthritis, which is often present in long-term injuries.

Treatment

• If the cruciate ligaments aren't completely torn, or if surgery isn't an option because of the dog's health, age or other reasons, vets will attempt to manage the injury with physical therapy. You will probably be asked to limit the dog's regular activities to allow time for healing. Your vet will likely prescribe a non-steroidal anti-inflammatory drug (NSAID) like aspirin or Rimadyl. If your dog is obese, he should go on a diet to attain a healthier body weight.
  If the ligament is too ruptured to heal on its own, surgery will be the likely outcome. If there is some ligament remaining in good shape, the surgeon might be able to reconstruct the cruciate ligament from nearby fibrous tissue. If that isn't possible, there are two types of surgeries for realigning the tibia to reduce mechanical stresses on the joint. Tibial plateau leveling osteotomy (TPLO) is the more common surgery. Tibial tuberosity advancement (TTA) surgery usually leads to lower rates of arthritis after healing, but the veterinarian surgeon requires special training and equipment that isn't always available.
  Prognosis is usually good to excellent, depending on the extent of the injury and the chosen treatment. A significant number of dogs will develop arthritis at some point as a result of their knee injuries, regardless of how the cruciate ligament injury is treated.