"I can't do squats because of an injury" is bullshiet. I hear it everythime in the gym, my back is bad, my knees are bad ect ect, but for some reason they can do every other legexercise. If u have a ingury, rest! Then start lifting light and slowely increase the weights. If your knee hurt, take a rest for 2 weeks and then go on, its not a reason for the shit for the rest of your life. How come almost every powerlifter get back after an ingury???
Pain is just a way for the body to say: Ok, I just need a little bit more time to recover.