The knee is a complicated joint. It consists of the femur(thigh bone) above, the tibia(shin bone) below, the patella (knee cap) in front. Cartilage cushions called the medial and lateral menisci fit between the femur and tibia absorbs the stress from activity. Many ligaments hold the complicated system together, allowing the knee to bend the way it should and keep it from bending the way it shouldn't.
There are two ligaments that cross inside the knee joint that form an X. They are called the anterior (or cranial) cruciate and the posterior (or caudal) cruciate. See the illustration. The anterior (cranial) cruciate ligament prevents the tibia from slipping forward out from under the femur and is the one most commonly injured (this is the same as the ACL in people)
A forward view of the canine knee joint. Illustration is public domain via Wikipedia.
How Rupture Happens
Two main scenarios are seen with cruciate ruptures. One is a younger large dog playing roughly who takes a bad step and injures the knee. This is usually a sudden lameness, especially if they were spayed or neutered before 12-18 months of age. On the other hand, an older large dog, especially if overweight, can have weakened ligaments and slowly stretch or partially tear them. The partial rupture may be detected or the problem may not become apparent until the ligament breaks completely. In this type of patient, stepping down off the bed or a small jump can be all it takes to break the ligament. The lameness may be acute but have features of more chronic joint disease or the lameness may simply be a more gradual/chronic problem.
** Larger, overweight dogs that rupture one cruciate ligament frequently rupture the other one within a year's time.**
Finding the Rupture
Diagnosing can be a little challenging since anxiety and amount of pain can influence evaluating the knee for instability but assessing for arthritis and range of motion can be helpful as well. Although x-rays can’t see the cruciate ligament itself, we can use x-rays to help evaluate joint swelling and degree of arthritis from previous cruciate strains.
Designing a treatment plan specific for each patient depending on the age, breed, activity level, and knee instability is extremely important. The plan may change over time depending on the progression of the cruciate tear. The following possible treatments but all may be used in conjunction with each other to get the most mobility and stability of the joint for your pet.
Recovery from the injury is difficult to predict and best left to the assessing veterinarian. Acute vs Chronic, age, weight, and degree of tear all determine the amount of care needed. One thing that can’t be helped is that eventually your pet will get arthritis in the knee and preventing it long term is the best treatment with keeping your pet at a lean weight, preventing pain, keeping muscle strength and preventing more instability being the most important.
What if the Rupture Isn't Discovered for Years and Joint Disease is Already Advanced?
A dog with arthritis pain from an old cruciate rupture will definitely benefit from physical medicine. Ask your veterinarian if it may be worth having a surgery specialist take a look at the knee. Most cases we can keep comfortable with medical management.
CONTROLLED EXERCISE - ON LEASH!!
Adequan Injections A series of Adequan injections can help with joint inflammation as well as lubrication. Typically injections are given twice a week for a total of eight injections.
Joint supplements Oral joint supplements contain cartilage building blocks to help the body repair cartilage damage. This is an excellent time to begin supplementation and there are numerous brands. Check with your veterinarian to see which are proven with research to work for your pet.
Weight Management Weight should be kept at a little below average weight. Overweight dogs have an increased risk for arthritis and for cruciate rupture. A weight management program can reduce the potential for arthritis and can reduce the risk of rupture of the opposite cruciate ligament. If your dog is overweight, ask your vet about a weight management plan that might be started during the recovery period.