However, when it comes to the knees, you need to throw that logic out the window. If there's anything in your body that you want to protect it's your knees. Think of you knees as Mother Nature's gift of shock absorbers to your body. With every step you take when running, your body receives an impact of several times your body weight. Your knees work to help absorb some of this force.
The problem with knee injuries is knowing what exactly is going on. It could be the knee joint or it could be the surrounding muscles, ligaments, cartilage or tendons or some combination of any or all of that "stuff." Best to let a sports doc determine the problem rather than guess your self.
I used to have an 18-year-old Ford Bronco II. That thing was ugly, but it sure was fun to drive. No air and it would hardly do 60 on the highway, but it was a good old truck. Every time we'd hit a bump in the road you'd feel it and go flying. My youngest used to sit in her car seat in the backseat and yell "Weedoggie" "YeeHaa!" "Do it again Daddy!" every time we hit a bump in the road. That is until the shocks went out. Oh man, then every time I hit those bumps, you didn't bounce, you just felt like you hit metal to blacktop. No fun at all. That's exactly what your knees can feel like once you've damaged your knees' shock-absorbing abilities. Problem is that you can't just drive into your local garage and ask for new shocks for your knees. The Bronco? Well, yeah, it lasted a few more years.
So, to avoid the Bronco II Syndrome, when you're feeling pain in the knee and it doesn't go away in a day or two, get yourself to the doc. Yep, he may say you have to stop running for a while in order for things to heal, but that's better than going to the doc after it's gone on too long and have him/her tell you to stop running altogether.
Running in itself is not bad for your knees. More and more research is showing that that old non-runner's excuse of "Oh, I don't run, it's bad for my knees" just ain't so. But, there can be things such as a biomechanical problems (like severe over pronation) that can contribute to extra stress on the knee which eventually will result in knee pain.
Mother Nature was pretty ingenious when it came to designing the knee. Your knees aren't just bone against bone. (That makes me hurt just to think about it.) In between those upper and lower leg bones and the petella is cartilage and something called the synovium. When you think of the synovium, think of a ball bearing. That's basically what it acts like in the knee. The synovium absorbs fluid called synovial fluid and it's this fluid that makes it so that the bones move smoothly over each other. There's even more cushioning called bursae. Bursae are fluid-filled sacs that are found around your knee joint. Actually you have bursae near or around most of the joints in your body. Ever hear of bursitis? That's a condition that happens when one of more of your bursae around a joint become inflamed.
Have you ever been for a run and then later when you try to get up your knee or knees have stiffened-up so much that you can't stand? Or maybe you've been on a long drive or sat in a movie and the same thing happened? If the stiffness is so bad that you can hardly stand, that's not just regular exercise-related stiffness. That could be something much worse called Plica Syndrome. Plica is tissue that sits around both sides of the knee cap. If you've ever fallen and landed on your knee, especially if you twisted your foot in the process and ended up with a sore knee, more than likely it's due to bruising of the plica tissue. A little rest and it usually heals and goes away. However, if the pain is the result of a biomechinacl problem like severe overpronation or maybe a really weak posterior chain (the muscle groups along the back side of your body - glutes, hamstrings, calves) this can cause your knee not to track properly which can inflame the plica tissue causing severe pain.
Some of you may be thinking...well it's just that tissue that's sore, no big deal. Well, if you let it go too long, it can definitely become a big deal. Over time, that inflamed plica can develop scar tissue and get thick. Once this happens rest and ibuprofen ain't gonna fix it.
So, let's back up a little... the biggest lesson from this post is, if you're knee hurts either from stiffness, soreness, dull aches or sharp pain....go get it checked. Better safe than sorry. Remember that old saying, "An ounce of prevention is worth a pound of cure."