"You don’t get to redefine the exercise and then claim that it’s dangerous. Driving a car is dangerous if you drive it into a great big rock."
-Mark Rippetoe, Starting Strength
Recklessly driving a car is bad; it's also incredibly stupid. Improperly lifting weights is bad; it too is also very stupid. Unfortunately, lifting seems to have a lasting stigma on so many people. "It's bad for your knees," they say. Perhaps it's because they don't enjoy lifting, or maybe they've never lifted, or it's possible they're incredibly insecure around lifters. Maybe I'm wrong. But what I do know is that when lifting is done right, there is far more good that comes from it than bad! Far more. When a car is driven right, the automobile serves a wonderful purpose, right? Or could you go about your day without it? (Public transportation folks, I hear you.)
Just for fun, here is one of 173 (I pulled that number from thin air, it's probably more) rebuttals we "lifters" can make about lifting being bad for the knees.
Sports and many of life's activities require abrupt stopping and quick turning. The impact of the immediate stop-go-turn activity can place a lot of valgus stress on the knee (see photo). On top of that, many of us are already predisposed to increased valgus; and, unfortunately, ladies actually have approximately 5 degrees more of this due to their anatomy. (Be careful the next time you're playing tag with the kids in the yard, ladies and gents!) How do we combat this? How do we lessen the likelihood of a sudden injury? We make the structure around the knee stronger. We lift! We deadlift and we squat.
There is something called the pes anserinus, and it is made up of three muscles, the sartorius, gracilis, and semitendinosus. These are muscles of the leg. According to the text Kinesiology, The Mechanics & Pathomechanics of Human Movement, "these three muscles together appear to contribute to the dynamic stabilization of the knee against valgus and rotary forces." How do we get these three muscles and their accompanying tendons stronger to withstand greater amounts of stress? Once again, we lift. We deadlift and we squat. Strength withstands greater stress.
Again, this is just one of *many* examples as to why lifting is beneficial to not just the knee, but the whole body!