I Have Extreme Pain In My Knees. Have Low Platelet Count

I m 22 years old and I m on presidnose to treat my ITP/low platelet count in my blood . I m taking 100mg per day and today, suddenly, at 4am, I woke up to extreme pain in my knees. The pain was sudden, sharp, and really intense. I could barely walk. I had to carefully hold onto things around me to down to the kitchen to grab ice to put on my knees, which at the moment is helping to subside the pain. I don t understand why this is happening. It is clear that my knees are really inflamed - and the only thing that I did differently today was to take Tums to treat heartburn . I m really scared because I read on another thread about a young girl with lupous, also on this medication, who took prednisone and wasn t able to walk. Does this cause arthritis? There are so many side effects - but losing the ability to walk is definitely a side effect that I cannot allow to happen; I d rather cease my treatment immediately and pray for my platelets to increase by a miracle . Does anyone know or have experienced something similar? Anyone have any insights, particularly about the arthritis bit?