We have come a long way in dealing with crooked knees, but we still have a way to goOnce upon a time, a foal with crooked knees (carpal deviation) was written off as a loss or, at best, a liability. Some were even put down. Some of these crooked foals would eventually straighten and some would not, and no one knew which would be which. And we still do not. Those that did not straighten, of course, were the problem.
A lot of corrective measures were suggested and tried. Corrective foot trimming was probably the first attempt to remedy the situation. It may have worked in some cases, but those were probably the ones that were going to straighten anyway. Even today, though, proper foot care is a necessary adjunct in many cases.
Braces or splints probably came next, followed by casts. Maybe some of these worked, but those that straightened once again probably did so in spite of the external devices rather than because of them. And these had the disadvantages of weakening the limbs and making it hard or impossible for the foal to get up or lie down, plus there was the possibility of abraiding the prominent areas over the joints; severe ulcerations resulted in some cases.
Surgery
In time, various surgical procedures were attempted, ranging from the simple and mostly ineffective to the bizarre, complicated, and mostly ineffective.
My personal favorite was one which involved removing a wedge-shaped section of bone, then turning it around and replacing it. I never saw it done, but I did see a drawing of it once. I suspect it was much easier to draw than it was to accomplish.
But, eventually, a moderately successful procedure was devised: stapling. Transphyseal bridging, I think, is the technical term. In this, metal staples are placed in the radius across the distal (lower) physis (growth plate) on the long side of the deviation. The theory is that this will prevent growth on that side while the growth continues on the other side. And it usually works.
But the staples have to be removed, and the timing is critical. If they are left in too long, the joint will end up deviating the other way as the unstapled side continues to grow. If the staples are removed too soon, correction will not be complete. It is necessary, then, to remove the staples just before the desired straightening is achieved. And those staples are often bears to get out. All of this has the disadvantage of two general anesthesias and two invasive procedures.
That brings us up to the present.
Periosteal elevation
A few years ago, someone came up with the idea of hemicircumferential periosteal transection and stripping, more conveniently called periosteal elevation (PE). This also requires general anesthesia and very minor surgery, but usually only once each, and does not require the placement of any foreign objects within the foal.
Timing is important. It must be done while there is still growth potential, but in the case of mild carpal deviation, it can be put off to see if Mother Nature will handle it. In severe cases, or those which seem to be worsening, surgical intervention should occur early, within the first 2-to-4 weeks, when there is still ample growth potential. Those in between-the wide, gray area considered moderate deviation-require more careful consideration and evaluation: To wait or not to wait. A good guideline to action is the degree of deviation. Five degrees or less, wait a while. Twenty degrees or more, hop on it as soon as possible. In between, PE will probably be needed, but do not be too hasty.
Coupled with PE, exercise should be limited, because it aggravates and worsens the deviation. Because the deviation causes uneven hoof wear, the hooves must be correctively rasped regularly, perhaps weekly in severe cases.
All crooked knees do not respond to PE. It may be necessary to repeat the procedure 6-to-8 weeks later, and it may also be necessary to staple some in conjunction with the second PE. But nothing is foolproof. Some will not straighten, no matter what we do. And, conversely, I suspect some that we operate on, even severe cases, would have straightened in spite of what we did. Someday maybe we will be able to predict both of these.