Many horses develop symptomless swelling around their fetlock joints known as windpuffs. These inflammations are soft to the touch and do not give off any heat. They are the result of increased fluid production by the deep digital flexor tendon sheath, and usually do not come with any associated lameness. Any swelling that is firm or warm to the touch should be examined by a veterinarian, as these are signs of an acute injury.  

Chronic windpuffs   Most of the time, windpuffs are a chronic condition of older horses. The result of sustained work or athletic activity, windpuffs will emerge many times over the course of a horse’s life without doing any real harm to the animal itself. The deep digital flexor tendon extends from the muscles in the upper part of the leg all the way down into the horse’s hoof. Along the length of the tendon, there are many places where it rubs against bone. In order to lubricate these connections and facilitate the movement of the tendon, there is a fluid-filled sheath that encapsulates the entire thing. This sheath will sometimes overproduce the lubricating fluid, resulting in the visible swelling that is characteristic of windpuffs.Though windpuffs appear slowly over time, they can sometimes seem to develop overnight. This may just be due to the fact that you simply never noticed them during their development, or it may be that the swelling has been caused by a torn tendon or ligament and isn’t a windpuff at all. If the horse is exhibiting decreased performance, then a visit to the vet is merited. However, if the swelling on the back of the leg doesn’t seem to be causing the horse any pain, then it is most likely a harmless windpuff.

Therapeutic treatments
While windpuffs are often only cosmetic blemishes that do not require serious medical attention, many owners choose to use soothing poultice on the swelling to reduce any discomfort the horse may be feeling. While it is unlikely that the horse is experiencing strong pain of any sort, a swollen tendon sheath often inhibits the proper function of the tendon itself, causing mild discomfort. Poultice is a fantastic external application for the temporary relief of that discomfort. The mixture of essential oils creates a soothing effect after events or racing. While you need not worry about true windpuffs, soothing external applications such as poultice are always a good idea for overexerted horses.