Oh GOSH! We were so concerned about the technical issues in getting this off the ground (while also traveling into a major winter storm here in the US) that I completely missed this question! Please accept my apology!
Wind puffs are an indicator that a strain has occurred to a joint. This is usually the fetlocks but it is also common in the hocks (where they are called a bog). The result of this strain is an increase in joint fluid that distends the joint capsule in a firm, fluid filled bulge around the joint. It is non-painful and usually does not cause lameness even with a flexion test.
Because these are sterile and non-painful, I avoid entering them with a needle to drain. If in the draining process the joint becomes contaminated, sepsis (infection) of the joint will occur which may lead to a permanent lameness.
Distinction of a tendon sheath looks similar but is not related to the joint. The name for the hind flexor tendon sheas the swelling is a “thoroughpin” while of the front flexor tendon there is no name. However, it is often confused with a wind puff of the fetlock joint. To determine which is which, careful palpation is needed. A wind puff is above the joint and between the cannon and flexor tendons. A distended flexor sheath is in front of and behind the tendons and rises higher than a distended joint capsule.
Please remind me of this question for the next AMA. Also, what are your thoughts in having a different time for you members on the other side of the planet? 7am my time? I could do that.