A common reason for filling is inactivity in a horse that is accustomed to moving around. An example might be a horse that is usually turned out in the pasture but has been kept in a stall overnight, maybe at a show or in preparation for an early ride the next day. The owner notices that the horse’s rear legs are puffy and swollen as he’s led out of the stall. The legs are not uncommonly warm, and the horse may move somewhat stiffly but is not truly lame. Caused by inactivity and reduced lymph flow, this “stocking up” is usually not serious and will dissipate as the horse is exercised. It’s more common in older horses and can affect all four legs, though stocking up is often seen only in the hind legs.
If your horse has leg swelling accompanied by lameness, warmth in the leg or hoof, or an elevated body temperature, it’s time to call the veterinarian. This is more than simple stocking up.
Swelling in a single leg is likely to signal a serious condition. Horses can “blow up” a leg in response to a scratch, cut, or puncture wound that may be so insignificant that it’s hard to find. The leg may be warm in addition to being swollen. This swelling isn’t likely to go down until the wound is cared for and any infection is treated.
A horse that has significant swelling in all four legs may have some type of systemic illness. This could be a sign of heart trouble, liver or kidney disease, or a bacterial or viral infection. It’s defintely a situation that calls for a veterinary examination.