RE: What can i do as a squat alternative
In truth, there are no real alternatives to the squat... There are a number of other lifts which you might consider comparable (deadlifts, goodmornings) but you are likely to have problems with you knee doing these as well.
How do you know you'll never be a good squatter? I would think that squats would help strengthen your knee, provided you start on a low enough weight and increase it gradually - Or has your doc/physio told you otherwise?