how often do you need to change running shoes

It depends on the individual. Many people change them at around 400 miles. I don't change mine until they become unservicable. My current pair has around 1450 asphalt running miles on them.

If you're not having any physical problems and the shoes are not falling apart then you may not need to change them.

right after I'm done running I usually change them.....:laugh:

I can only get 400-450 miles out of mine - after than I feel like I am getting shin splints. I run out of two pairs (same exact model) at a time - I rotate each run.

Your mileage may vary...

It depends on the individual. Many people change them at around 400 miles. I don't change mine until they become unservicable. My current pair has around 1450 asphalt running miles on them.

If you're not having any physical problems and the shoes are not falling apart then you may not need to change them.

I'd LOVE to get 400 miles out of mine!! I get 250 miles and after that, I start feeling it in my knees, ankles and/or feet. 6 months isn't a bad estimate. But it depends more on the mileage than the days used.

could it be the way i run as to why my knees are sore

Google "Good Form Running". My knee pains went away when I adopted that running form. Essentially you should avoid overstriding and plant your foot under your center of mass on each step. It reduces the impact forces to the bones and joints.

Depends on the shoes. Barefoot shoes don't need to be replaced until they literally fall apart and are unwearable - thankyou merrell for being honest about this fact and not maintaining the "6 months" rule that would mean consumers spending more $

As for whether or not barefoot is for you, you just have to try it - but it could be worth it in the $ saved not buying shoes every 6 months or forking out for expensive arch supports and physio sessions. last year I developed runners knee and basically quit running. my physiotherapist said I needed to get custom arch supports ($400) and wear full support shoes (usually around $200). I didn't have the money, but then my sister gave me the book 'born to run'. Immediately after I bought my first pair of merrell barefoot shoes ($125). It meant going back to the beginning and learning how to run all over again; I was slower, couldn't run as far, my feet were really sore after each run and my calves had some muscle building to do, but according to merrells guides on barefoot running these were good feelings. They meant I could tell when I was pushing too much, and stop before I injured myself. Two months later I ran my first marathon in them, injury free and no sign of my previous runners knee. It's been 1 1/2 years and my shoes are finally dead and I haven't been back to physio since. Pretty good for $125. If you want more info on barefoot merrell has a lot - for free - on their website.

Depends on the shoes, usually 6 months for me.

Runner's World Magazine writes,

"Between 300 and 500 miles. Why the range? Because how quickly a shoe wears depends on you. If you land hard on your heels with each stride, for example, you're going to wear through shoes more quickly than more efficient runners. Go by feel. If after a normal run your legs feel as if the shoes aren't providing you adequate protection, they probably aren't. Give your legs a week to make sure it's really the shoes and you're not just tired. If the shoes still feel dead, replace them. We can tell you that the vast majority of runners replace their shoes too late. When you can see white midsole material poking through the outsole or when the sole under the heel looks crushed, the shoes are long past their prime."

Right off their web site.

I have 310 miles on my Saucony Mirages and they still seem pretty new to me!