A windpuff is a soft swelling usually found on a horse’s fetlock. The remnant of an old injury, it occurs when inflammation stretches a tendon sheath, bursa or joint capsule and then subsides. The structure remains stretched and fills with fluid. A “set” or mature windpuff is of no consequence beyond its cosmetic effect. 

To determine whether a swelling is a windpuff or something more serious, consider these factors:

1. Its onset. A swelling that appears suddenly is more likely the result of a recent acute injury. But even a windpuff that “just appeared” may have gone unnoticed for a time. 

2. Its feel. When a horse is standing normally, a windpuff is soft with the consistency of jelly; there is no heat. When the affected leg is weighted (ask a helper to rock your horse until he leans on the limb), a windpuff may feel more like a marshmallow. 

In contrast, an area of active inflammation is more likely to be quite firm when the leg is bearing weight and may be warm to the touch. 

3. Whether your horse is lame. The initial inflammation that is responsible for a windpuff often causes temporary lameness. But a mature windpuff does not make a horse sore. 

4. His reaction to a flexion test. Tightly flex the fetlock for at least 30 seconds, then have a helper immediately jog your horse away from you. A mature windpuff will not affect gait.