Genu valgum is the Latin-derived term used to describe knock-knee deformity in which the knees are abnormally close together (knocked). The knee or stifle may develop a twisting away from the midline (genu valgum) if there is asynchronous growth of the bone at the lower growth plate of the femur. Some animals develop this deformity due to hereditary or genetic disorders or metabolic bone disease. The typical gait pattern requires that the individual swing each leg outward while walking in order to take a step without striking the planted limb with the moving limb. Not only are the mechanics of gait compromised but also, with significant angular deformity, anterior and medial knee pain are common. The condition begins at about 3 to 4 years of age and is most common in giant breeds.
Causes of this condition are thought to be associated with new bone tissue that is laid down rapidly and before sufficient blood vessels are established within the bone tissue to supply adequate nutrition to this growth. It is often seen in dogs affected by lateral patellar luxation which occurs in both large and small dogs. When it is present bilaterally the animals have a crouched genu valgum-type stance.
Several nutritional imbalances have been implicated in development of genu valgum. Experiments in human subjects have shown that high intake of molybdenum affects copper metabolism. Moreover, in areas where the incidence of genu valgum was high, the copper content of water was found to be very low as compared to that in non-genu valgum areas. An outbreak of genu valgum (knock-knees) in India was attributed to an increase in molybdenum and excess fluoride levels in sorgum, the main staple food of the region. Both copper and fluorides have a role in bone formation, and molybdenum promotes fluoride absorption.
- Big Dog Breeds. Dan Rice, D. V. M. Dan Rice
- Sorghum and millets in human nutrition. Nutritional inhibitors and toxic factors (FAO.org)