Angular Limb Deformities in Dogs

Angular limb deformities are common in dogs. An angular limb deformity means that the spatial alignment of a limb is abnormal, leading to pain, discomfort and often, lameness. This may be due to injury or be hereditary.

They are seen primarily in dogs of chondrodystrophic breeds. Chondrodystrophic dogs have a genetic make-up that leads to variable impairment of the growth of their appendicular skeleton and skull. Their axial skeleton is spared. Most chondrodystrophic dogs have symmetrically deformed forelimbs and pelvic limbs.

The most frequently diagnosed limb deformity in canines is called an angular valgus forelimb deformity (toe pointing outward). It develops secondary to unequal growth between the two bones in the lower forelimb (radius/ulna). This usually arises secondary to a growth plate (regions near the ends and tops of bones responsible for bone growth) injury.

Causes of Angular Limb Deformities in Dogs

The forelimb has two bones between the wrist and the elbow joint: the radius and ulna. The cone-shaped growth plate of the ulna, located near the wrist, is particularly susceptible to becoming injured. When this happens, the ulna ceases to grow because this one growth plate is responsible for about 90% of the bone’s long growth. This forces the radius (the larger bone of the foreleg) to deviate because the two bones are bound together by ligaments. The ulna bone will be shorter than normal and results in a “bow-string” effect in which the radius becomes twisted and bowed.

The cause is most often trauma, such as car accidents or being stepped on. Younger dogs whose bones are still growing – especially large and giant breed puppies – are at much greater risk for developing a severe deformity than older animals after a traumatic injury

Symptoms of Angular Limb Deformities in Dogs

For dogs that typically have short, bowed limbs, a common sign of a problem is limping on one or both forelimbs. While deformities can occur in the hind limbs, this is less likely (with the exception of Dachshunds).

Should your dog not be from a breed that typically has bowed legs, if you notice a visible limb deformity, lameness or a reduction in motion, you will want to bring your dog to the veterinarian for an evaluation as soon as possible.

Diagnosing Angular Limb Deformities in Dogs

Angular limb deformities are diagnosed with a physical exam and x-rays. On physical exam, the patient’s gait is observed and the joints adjacent to the deformity are palpated. Pain, swelling, and reduced range of motion may be identified. Precisely positioned x-rays are used to assess the exact location. The type, and severity of the malformation, and to evaluate its impact on the associated joints.

Treatment

Early intervention is critical for a good outcome, particularly if the puppy has a significant amount of growth yet to achieve. If there is lameness, intervention is more important. Some patients will respond to nutritional adjustments. Too much protein and fat in the diet or adding calcium and/or phosphorus can contribute to angular limb deformities.

Surgery is often necessary to straighten bones affected by an angular limb deformity. The type of surgery performed depends on the individual injury, the bone(s) affected and the patient’s age and growth potential. Often, the abnormality in the limb is severe enough to warrant more than one surgery to repair it.