Why does my knee/back/neck/foot/shoulder/etc. hurt only sometimes?
Pain that goes away, doesn't mean that there is no problem. Sure there are aches and pains that come and go. But if you notice that your knee hurts going up and down steps often enough, then this is a sign of a problem and the more you ignore it, the greater the problem will become. Pain does not just go away or fix itself; your body just makes it seem like it does.
The truth is that before pain becomes constant there are lots of warning signs that people ignore. People who wind up with chronic back pain, often remember spasms that started once a year, that would put them on the couch. Then the spasms increased to happening once a month and then came on weekly and it took longer and longer for the spasms to calm down. If pain is increasing in frequency, intensity or duration, it is a problem. The longer you ignore it the longer it takes to go away.
How does the body let this happen? Your body is very smart and is able to compensate for pain. Let's use the knee, for example. The pain may start with running but after you're done, the pain goes away. When the body feels pain it will do everything it can to make it go away. Your body will change the way your foot strikes the ground (without you even realizing it) and with this small change, it will change the way your muscles and bones are used. This change in foot position and use of muscles, will allow for the pain to subside. Other muscles will take over for the sore muscles, allowing them to recover.
Moving forward, each and every time you run your muscles will compensate and allow the sore muscles to relax. After a while, the muscles that are compensating become retrained to work improperly all the time. As these muscles work incorrectly, the pain begins to intensify and you feel it with more activities than just running. Then the muscles begin to form another compensation pattern to try to decrease the new pain. This is a snow ball that continues to roll. Eventually the muscles are not able to compensate any more and you have pain all the time.
How do you prevent this from happening? The general rule I give to my patients is that if you feel pain for more than 2 weeks, it is not going to go away on its own. You need professional help and the longer you wait, the longer the treatment will take.