Hello there.... yes definately Physiotherapy would be of immense benifit to your father...however before commensing any treatment take X-ray of both knees in lat/AP posn.. & please check his calcium and D3 levels if found below the normal range then appropriate supplimentation can be started... static and active dynamic exercises could be of great help combined with close chain kinematic exercises like crosstrainer or static cycling...depending on his pain threshold IFT vector 90 may be required....also patellar knee cap for the affected knee would be of great help to him. Do let me know regarding any furthur queries Regards,Take care.