My wife has had PD for 10 years now. A few weeks ago also confirmed she now has PDD and going on medication for it this week comming. In June the parkinson nurse at the hospital increased her parkinson meds. This last month she has had problems balancing more than normal. I contacted the parkinson nurse at the beginning of the week and was told to take her for a blood pressure check at the doctors just in case it was dropping when she stood up. The test at the doctors proved ok. This last few days she has got to the stage where she can not stand up with out someone holding her up. She can not even stand up and walk with the frame. Has any one else come across this and knows what could be causing it or is this the final stage of parkinson's. She is still eating ok and can still feed and dress herself with help sometimes. Her upper body is ok apart from speech and parkinson's face. It is just her legs that will not support her.

How distressing this must be for you both. I would certainly ask for some physiotherapy treatment. In my experience holding the spine in fixed or certain positions over prolonged periods only adds to any problems, so the more active the better.
Noticing a month has passed from you posting this thread, I hope the PD nurse or GP have already organised something.

Best wishes Andy