What Is The Permanent Cure For Knee Pain?

Hi. My mother (age 50) had a fall and has hurt her right knee. The pain is mainly in the back part of right knee cap. The pain is felt whenever she bends her knee after standing/walking for a while or while standing up after sitting for sometime. It has been over a month and she has been prescribed Zerodol P. The tablet gives her relief for a day or 2 and the pain restarts. Is there a permanent cure? How long can Zerodol P be taken without any damages?