When newborns stand up for the first time, their limbs frequently have several abnormalities. Many of these are related to laxity of ligaments and tendons and will correct in the first few days as long as the foal can get up and move around normally. You can divide these abnormalities into two main groups, depending on whether you can see the abnormality while standing in front of the foal or from the side:

• A deformity best seen while looking at the side of a foal involves the flexor tendons: see Flexural Limb Deformities of Foals.
• A deformity best seen from in front of the foal, as pictured below, is an angular limb deformity and dealt within this article.

With angular deformities the normal straight line of the leg when viewed from the front has a bend in it. The deformity can occur in any joint of the leg but is seen most commonly in the knee (carpus), fetlock, or hock (tarsus). Severe bilateral angular and flexural laxity may result in a foal that is called "wind swept." There are several common causes of the problem. The treatment and prognosis are dependent of location and severity of the problem. This article discusses the diagnosis, treatment, and prognosis of angular limb deformities in foals.

Angular limb deformities are a common orthopedic disorder of horses. Some surveys find an incidence as high as 5% of foals are affected to the point of needing treatment. The most common deformity is in the knees with the cannon angled outward (carpal valgus). At birth a straight knee is uncommon but the large majority correct themselves over the first few months of life. Any joint can be involved however.

The joint affected, the direction of the deviation, the amount of deviation, the age of the foal, and the cause of the deviation all effect treatment and prognosis. We usually localize the deviation to a specific structure by using the upper limb as the ruler and dropping a bisecting perpendicular line past the approximate level of the deviation. A similar bisecting line is projected proximally from the deviated long bone. Where they intersect is the level of the deviation. Such localization often is diagnostic for a particular cause of angular limb deformity. Limbs that deviate away from the body are called valgal deformities. Those that deviate toward the midline of the body are called varus deformities.

Once the joint or area of deviation is identified radiographs help identify the cause of the deformity. Usually accompaning angular deviation is some degree of rotational deformity. With valgal deformities the limb generally rotates outward and with varus, inward. Correcting the angular deformity will usually correct the rotational problems.