Suggest Treatment For Pain In Knee After Surgery

Hi Doctor, i am writing on behalf of my mother, she is 62 yrs old, wt 67 height 5 1 ..She was diagnosed with oestoporosis couple of years back and has been under medication for the same, she had fallen down and broke her Left knee cap couple of years back and surgery was done to fix it...it was a successful surgery and all doctors have given a thumps up on complete recovery...however since last 4 months she has been stuggling to walk with her left leg...she has pain which initially started from hip to left feet toe...no pain in right leg..pyshiothery was done and now the pain has subsided but from knee below she has constat pain while walkin...if she sits and takes rest nopain...pysiotherist mentioned that this is due to nerves not able to support the bone structure....now request you to suggest what needs to be done and what is the diagnosis?? pysiothery is stoped for last 2 months and mild exercise is in progress...she could not move arnd initialy but now movement is der but limited as little exertion on the left leg gives emmense pain...