Hi ski=free! Just be glad it was MCL, not ACL. The first post in this thread has some excellent mogul advice: http://forums.epicski.com/showthread...=lesson+mike_m
That being said, there is a specific problem with moguls that is not technique related. It's called mogul addiction. Once you start to ski them half decently, you want to ski them all the time. Sometimes, your choice of when to ski them is simply inappropriate, such as the end of the day when you're feeling tired.
As Ron White said, always "rehearse" you mogul technique on the groomers. You can even practice a series of pivot slips leading down to the mogul trail. Here is a common mistake that can lead to injury, which I unfortunately got to experience through "empirical research."
Just like regular skiing, you want to turn your skis up the hill. Unfortunately, if you are tired, that sometimes translates into leaning into the hill. This can either put you in the backseat, which might be the catalyst for an ACL injury, or cause a twisting action which can damage the MCL.
Also remember that mogul skiing demands a concise blend of visual and physical skills that are facilitated by proper breathing technique. Last season, Mike had us "cross-train" for moguls by doing some easy tree skiing. We were taught to look at the opening outside the trees, not the trees themselves. The same applies to mogul skiing. Look where you want to make your next turn. I got hurt by focusing on a classmate that had stopped short in the middle of a crowded mogul field. I was trying not to hit her, but my focus lead me right into her line. Since I was tired, I freaked out, leaned into the hill, wiped out, and slid in her direction.
I had also neglected to use breathing. I don't want to get into a "where to breath" debate. Just choose a method and use it.
I hope you found this helpful. As for me, all I can say is that there sure is clarity in hindsight!