I have been experiencing pain in my right knee whenever i walk over a few miles. sometimes i won't get the pain at all. it also hurts more going down ?

Soft tissue strain: It is probably related to one of the supportive ligaments/tendons that are around the knee joint. If it is not constant, then it isn't severe, and you can try resting it for a couple weeks to let the problem heal itself. When you walk, especially long distances, be sure to wear proper footwear. If the problem worsens or persists, a course of physical therapy may help.