Suggest Treatment For Difficulty In Flexing Leg Muscles When Diagnosed With Fibromyalgia

I am a 57 year old female, diagnosed with fibromyalgia about 5 years ago. As an accountant I am required to sit for long periods of time. Over the last year I ve had increasing difficulty rising from a chair, walking, and using stairs. A few months ago an Orthopedic Specialist diagnosed me with degenerative meniscus fraying with a small medial tear after reviewing MRI results. I had a cortisone injection 5 weeks ago and I ve been in physical therapy for 3 weeks now. While the knee pain, range of motion, and ability to walk have continued to improve nicely, I am still experiencing significant difficulty walking, primarily after sitting, and using the stairs. When rising I feel a deep ache up and down both legs, I stand for 20-30 seconds before beginning to walk but I m still so stiff and unsteady I m concerned there might be another issue going on besides just the one knee. Should I give it more time (how much more time) before I go back to the Ortho Specialist, or should I seek a second opinion from someone else in a different field of expertise?