Anatomically, the fetlock joint is not really the horse's ankle at all. It is the metacarpo-phalangeal joint of the forelimb- the equivalent of your middle (upper) knuckle joint. (The hind limb fetlock is the equivalent of the middle metatarso-phalangeal joint at the front of your foot.) The fetlock is an extremely dynamic and sensitive joint- a very high-motion, critical component of the intricate mechanism of the lower limb of the horse.

Swellings around or involving the fetlock are common. In the horse world, swellings here are often known as "wind puffs", "wind galls" or "road puffs."

In performance horses, benign swellings develop over time and are usually not cause for worry. These are the so called wind puffs and they are usually present in multiple limbs and tend to be more obvious in the hind limbs. These swellings should be cool to the touch, non-painful and not be accompanied by lameness.

In contrast, one-sided swellings that appear suddenly, are warm to the touch, are accompanied by lameness and possibly reduced range of motion, or poor performance raise greater concern and need to be evaluated by your vet. Injuries do occur here, and they can be serious. It is important to know that there are two structures at the fetlock that usually become filled with fluid: the fetlock joint itself and the digital flexor tendon sheath. Swelling in one or the other of these structures means something different.