Lameness in Dogs

Novemeber 11, 2011

The cranial cruciate ligament (CCL) accounts for the majority of stifle (knee) Lameness in dogs. There can be a total or a partial tear either of which sets off an inflammatory reaction in the stifle that leads to arthritis if the condition is not corrected. The cruciate ligament is made up of two bands, the craniomedial band, which is taut throughout the range of motion, and the caudolateral band which is taut only in extension of the joint. The function of the CCL is to prevent the femur from slipping backwards on the tibial plateau and to prevent internal rotation of the femur relative to the tibia. A complete tear occurs when the foot is planted on the ground and the pet rotates quickly (to the right tears the left, to the left tears the right) like you see when a dog chases a ball, goes past it and turns abruptly to go back to get it. A partial tear occurs when the stifle is hyper extended and stressesthe caudolateral band.

A torn CCL is common in both large and small breeds but causes the most problems for large, long legged dogs. Large breeds that are spayed before they reach maturity lose the sex hormones that are responsible for closing the growth plates. As a result, the bones continue to grow and the pet tends to be taller, lighter boned. The femoral growth plate closes at 8 months and the tibia at 12-14 months. If the tibia continues to grow for 6 months longer than the femur, there is disparity between the bones lengths that may cause increased stress on the CCL.

The average age of dogs with a torn CCL is (six) years. Males and females are equally represented. Spaying and neutering as a contributor is controversial, but in our practice, we see more spayed/neutered dogs with the problem especially since animal shelters are spaying and neutering dogs as early as two months of age. Being over weight certainly is a contributor because for every one pound of extra body weight you add five pounds of stress to the stifle joint. Being fed a premium diet may be a factor also. The breaking point of the CCL is thought to be four times the weight of the dog.

The torn CCL is diagnosed by physical examination and radiographic signs of joint inflammation. The "sit test" is an important part of the physical exam because a dog with a torn CCL tends to place the affected leg to the outside of the body rather than having the stifle flexed with weight directly on the joint. The presence of a medial Buttress (which is a thickening on the inside of the joint) is a sure sign of a CCL tear. Complications are the presence of arthritis at the time of the diagnosis and a torn meniscus which can occur before surgery with the original injury or in some dogs from months to years after the surgery. A meniscal release which is done by cutting the meniscus to “free” it to move as the femur places weight on it, reduces the incidence of torn meniscus after surgery from about 10%, to about 2.5%.

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Lameness in Dogs

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