Genu valgum is a joint deformity that results in the knees of a dog's hind legs bowing toward each other, making walking difficult and sometimes painful. Genu valgum affects giant breeds such as Great Danes, Saint Bernards and Irish wolfhounds. Sometimes the condition will resolve on its own; in other instances, dogs will need corrective surgery.
Genu valgum most often affects puppies between 4 and 6 months old, a time of rapid growth in giant-breed dogs. The patella lays too far to one side or the other in the joint, forcing the knees together and the ankles outward, eventually leading to patellar luxation and hip luxation. Over time, the condition can cause the cartilage in the joints to wear away, leading to arthritis, and may lead to atrophy of the muscles due to a reluctance to walk.
The cause of genu valgum is uncertain, but veterinarians have several theories. A difference in the speed that the growth plates expand may lead to the condition. A failure of the cardiovascular system or skeletal system to meet the rapid growth needs of these breeds may also be to blame. Puppies being fed an excess of protein, calcium, vitamin D and vitamin C appear to be at risk of genu valgum.
Depending on the severity of the condition, you may notice anything from the occasional skipped step or lifted limb to extreme lameness and a crouched walking position that shifts weight from the hind legs to the forelegs. Your vet will most likely feel the knee and hip joint to see if there is any luxation, movement outside of the joint socket. An X-ray is also commonly used to examine the bone and joint structure to help make a full diagnosis.
Some puppies will recover completely on their own and need only to be offered painkillers and proper nutrition to help them get through the uncomfortable time. If surgery is necessary, it must often wait until the puppy has finished growing, since further growth could disrupt the surgical changes. As many as three surgeries may be necessary, one to repair any bowing in the femur, one to position the patella in the joint, and one to correct any malformation in the hip.
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