physical therapists use that theory a lot, problem is it will work on old farts but with us it will ABSOLUTELY fail miserably 95% of the time
as weight lifters our injuries are typically more chronic in nature because we pound away. also our muscle imbalances are very different because we are so much stronger and conditioned. this is why going to a physcal therapist for an injury for us rarely helps because they will have you do 'band work' and ridiculous things like that.
i would be very wary of your shoulder pain, that could be a rotator issue and it won't get better any time soon. as far as your knees you need to listen to your body there. i would grab some n2jointrx