Knock knees (carpal valgus) is the horseman's term for angular deformity of the horse's carpus. In horses with this conformation problem, one or both carpi (improperly known as knees) deviate inward toward the opposite one. Like other conformational defects, knock knees occurs in both foals and adults and can range from mild to severe.

In adult horses, this is a fairly common conformation fault especially in narrow chested horses. If there is obvious outward angulation and/or rotation of the cannon, fetlock and foot, it may predispose to tendon and ligament injuries and carpal arthritis.

In young foals and growing horses, this deformity may self-resolve as the horse grows. However, in more severe cases or where this abnormality is accompanied by lameness, there may be opportunity to modify growth at the growth plate (with surgery) to help the situation.

Diagnosis is by visual assessment. Radiographs (x-ray) help better define the nature of the problem and at what level and anatomic structure the angulation is actually taking place.

Treatment depends on the specific case. In adult horses, conformation may or may not be a problem depending on expected level of performance and nature of work. In many young horses, treatment is not needed at all. Exercise restriction of young foals may prevent overload of the limbs and encourage the natural tendency to straighten over time.

In growing horses, angular limb problems should ALWAYS be evaluated early. Depending on the specific anatomy involved, the lower radial growth plate is not surgically treatable in horses over 18-24 months of age because the growth plates have fused and are no longer lengthening.