I have knee pain after i bend my knee."

Insuff information: You are young to have arthritis, and I have no other past medical HX. Best to see an orthopedist. Has there been a history of trauma to that knee? Are you involved in any sports where you may have inflamed your patella tendon? Do you commonly wear high heels? This is something that needs to be examined for diagnosis.

Knee pain: Pain in any joint is a signal that something is not 100. % normal. Use pain as a guide of what not to do . Eg if walking on stairs produce knee pain , limit that activity. If after a few days of rest , ice , NSAIDs ur knee is not improving , then u should be seen

Patellar pain.: Could be pain related to the tracking of your kneecap. See a non-surgical sports medicine physician to determine the root of the problem.

Varies: Multiple potential causes including pain from chondromalacia under the knee cap to things like a knee effusion. I would not hesitate to be seen for an accurate diagnosis.