Windgall, or windpuff, is the term used to describe the soft swelling seen just above the fetlocks or the forelegs and hind legs of typically older or harder-working horses. The term refers to either an enlargement of the fetlock joint capsule (an articular windgall) or an enlargement of the digital flexor tendon sheath (a non-articular windgall).
Formation of windgalls
All equine joints contain lubricating synovial fluid within a sac or capsule to prevent the fluid from leaking out under normal circumstances. This fluid protects the joint and allows it to move smoothly and easily. In the case of the fetlock joint, the synovial capsule extends out of the back of the actual joint and forms a pouch above the sesamoid bones behind the cannon bone. If the pouch of the joint capsule becomes thickened or swollen with excess synovial fluid, the resultant swelling on the back of the fetlock is described as an articular windgall.
The tendon sheath, in contrast, is entirely unrelated to the joint and is basically just a tube of fluid that envelops the tendons as they run over the back of the joint. At the upper limit of the joint, just above the sesamoid bones, the sheath lies close to the skin, so that any distension of this sheath secondary to thickening of the membrane or excess synovial fluid will cause a bulge between the flexor tendons and the suspensory ligament. This is a tendinous windgall.
The two types of windgalls
Tendinous windgalls
Of the two types of windgalls, the tendinous windgall is the most common and the least likely to reflect any real trouble. Tendinous windgalls are commonly seen in middle-aged horses who have had a hard-working life. Tendinous windgalls often come and go, and are generally speaking little cause for concern. They rarely result in pain or lameness.
Articular windgalls
Articular windgalls are more likely to be an indicator of disease, as they commonly occur in cases of degenerative joint disease of the fetlock and in certain traumatic conditions. They are closer to the capsule of the joint and are found in a more forward position. They are also, however, seen in a great number of ‘normal’ horses who never show any signs of lameness, appearing as firm bulges on the back of the cannon bone and the suspensory ligament.
Many showjumpers, eventers and ponies develop stiff fetlocks, which cannot be passively flexed to the normal extent and carry articular windgalls all of the time. These horses appear to cope surprisingly well with these inflexible fetlock joints, but the stiff joints are still likely to have some performance implications. This stiffness is quite characteristic of windgall issues, and when pain and lameness become apparent, it is actually far more likely, that rather than dealing with a primary windgall issue, you are instead dealing with pain resulting from the original cause of the windgall, such as the degenerative joint disease.
Part 2 to be released tomorrow