What do you do if you can't perform squats? My knees are just to week. Dislocation several times and they feel they might do that with the squat. I do extension and curls, with sit down squats-the kind where you are sitting and push the weight up. If I can't perform the squats, am I destined to not have muscular legs? Rock

No, you'll be fine. I can't do squats either cause of my back. I stick with the leg press and the others you mentioned. My legs are just fine :).