One other thing to consider is that if lifting heavy is causing you to have low back and knee issues thus not allowing you to train (legs anyway) then why not go lighter and concentrate on the muscle and maybe your joints will no longer hold ya back and you may also find that your legs do in fact grow from this type of training.
Lee Haney's old adage "train to stimulate not annihilate" may be the words of advice/wisdom that you may need to follow at this point.
I agree with you both on this. I learned a long time ago that you should never lift heavier than what your joints will allow you to. What this means is that if you are throwin' weight that is causing "hard" or real pain in any given joint related to the movement related to that joint, then you are well over the max stress load for the same, even for a "injury-free" body...of coarse we all feel pain during the first 2 or so "working" sets (even after a good warmup routine), but when the pain does not go away but persists, this may signal an underlying injury. Another lesson I have learned through trial and error is when working with heavier than normal (MAX) weights, NEVER go for a full stretch or lock-out, always move the weight slowly and deliberately, and ALWAYS save some for the recovery and even the next training session (this is why I simply love the "5 x 5" routine). I'll do it 4 or 5 times a year for 3 or so weeks at a time and that's it! I beleive that one does not have to constantly lift big to be big. Hell, even Ronnie and Jay will agree to this! J.
