Re: How do I stop my knee from buckling during a jumpshot?
sounds like you have some muscle imbalances, exactly what I cannot say but those are tell tale signs that you need to strengthen your body (im not talking getting jacked, I'm saying strengthening your weak/support muscles)
In terms of stance, it is simple. Head over shoulders over hips over feet. 10 toes to the hole. Forget feet position for a second. Before feet position comes balance. Without balance you are doomed to have an inconsistent shot. Chances are this is your problem (probably another reason why your legs feel weak under your shot).
Do you do any core work? Try doing a core circuit 2 or 3 times a week for three weeks and see if this problem persists. If it does you probably have deeper issues that need resolving.