I broke my fibula 8 weeks ago. I got my air cast [email protected] 6 weeks and was told to start weight bear slowly everyday. My knee hurts when I do. Why?

Fibula head pain. I assume you broke your fibula at the ankle. (and not proximally at the knee). At the time if fracture the mechanism of the fracture could have caused what is caused 'translation' of the fibular head at the outer part if the knee. This can cause knee pain. If this is the site if knee pain then see a physiatrist (rehab medicine) for ultrasound treatment along the outer part if the knee. Goodluck.