Suggest Treatment For Pain In Knees And Legs Along With Weakness

i have been having pain in knees and legs very weak legs as well...I have a job that i stand for almost 8 hrs a day and sometimes it is an effort just to walk . I also have a balance problem where is i am kneeling or squatting i can topple right over. I am very concerned about this. I have had DVT before and just checked again and that is all clear.. have also had surgery for torn miniscus.. the inside of the knees seem to be swollen and chafed?