What Does 'hot Spots' In The Knees On Bone Scan Suggest?

I had a bone scan today d/t chronic pain in my feet for MONTHS! Many dr. visits and Podiatrists have left me frustrated with NO results. The most recent doc ordered a bone scan. I noticed today that the pictures on the monitor in the Nuclear Medicine room had MANY bright white spots on the screen. Especially in my knees. (I have recently had a lot of knee pain as well). SO....I am wondering what all those HOT SPOTS or BRIGHT WHITE areas indicates? Thanks in advance.