Hello Doctor, My Mother Has Osteoarthritis Knee And Her Doctor

Hello Doctor, my mother has osteoarthritis knee and her doctor advised cartigen forte once a day for 12 weeks. She took it for a month and then forgot about it . She hasn't been on cartigen for the last one month, if she wants to re start cartigen, should she take it for 2 remaining months or whether she has to re start 12 week cartigen therapy?