Hi Marlene,
If the MD is affecting your quadriceps (the front of your thighs) then yes, you will feel as if your knees will buckle. My LGMD has affected my quadriceps. This is one of the most used and most important muscles for standing, walking, running and climbing. To test this, sit in a chair then try to stick your feet straight out and hold them for a few seconds. A healthy person can do this easily. I can't do it at all. I can only stand and walk with my knees locked.
In the early stages of muscular dystrophy, I used to tell people "Walking feels strange" or "kicking a ball feels strange". That's because the healthy muscles are just beginning to be affected. Now, 7 years later "strange" has become "very difficult". Believe me, I understand what you're going through with all the fear, frustration, embarrassment, etc.
Myotonic Dystrophy can also affect your face and hands in some cases. That could explain the tightness in your forehead. Best of luck.
Mark