I fell over when running and now my knee is swollen and painful, have i broken it?

Knee pain: You possibly may have torn a ligament or cartilage. You should see an orthopedist. It was difficult to break the knee

Sprained Knee: Good day; Most likely just sprained ligaments around knee. Take 400 mgs. of ibuprofin 3-4 times a day. Elevate your leg so your foot is higher than your knee a few times a day and ice the knee every few hours. Attempt to gently increase range of motion daily. Expect improvement on a daily basis.

Possibly: There are multiple possibilities, including that you sustained a fracture. I would not hesitate to be seen and thoroughly evaluated for your injury.