I had a torn miniscus in 2008 that was repaired. About a year ago it started hurting on the back side. When I bend my leg it fills swollen?

Knee effusion. A knee effusion or swelling of the knee will cause pain and stiffness on bending. You should be evaluated by your orthopedist for the reason why you are swelling and to initiate treatment. In the meantime ice, elevation and anti-inflammatories may help for the pain and swelling.