knee pain during running

Question
Hello, I develop knee pain when running on the tarmac. This generally happens after 3miles. However indoors, on the tread mill I am able to run much longer, 6miles before which i develop pain. The pain mainly develops in the left knee first. Once the pain develops, I have to stop running, climbing stairs is difficult. The pain recedes after a day or two. I have been informed that my foot is rather flat which may give rise to problems. Additionally I have ruptured my achilles tendon in the left leg in the past. Kindly advice. Thank you.

Answer
Hi

It could be a few different things. It could be a form of tendonitis or more likely it is due to your form. If you are extremely flat footed and do not have orthotics, it could lead to pain. It may affect your natural form and cause pain. you can solve this through seeing an ortho and possibly getting orthotics for your shoes. This could also cause tendonits if you actually have tendonitis. Another cause may be that the ruptured Achilles has changed your form. This again can be fixed through orthotics. See an ortho and see what he suggests. My guess is you need orthotics.