My Dad is 85 and has been struggling to stand up and move more this year than ever but last night that changed from difficult to not at all?

Please bring dad to the ER for evaluation. This is NOT a question for a forum of strangers to answer.

Good luck to you.

Any sudden change needs medical attention. My dad had several years of increasingly weak legs, which despite many rounds of physical therapy, remained and steadily worsened. Standing up and walking both difficult for him, aided by a rollator. His was likely linked to congestive heart failure as his heart became a poor pump, his extremities weren’t getting fully oxygenated and became weak. There are many possibilities. Please get your dad seen as soon as possible.

He might have an undiagnosed neurological disorder. Some can be very serious. I have 2 ideas but I am not a doctor. Is he living alone? Does he have at least 2 carers living with him? This is not safe. This is new. Doctor appointments might take a while. You can take him to the ER since this is sudden. But take him to a larger facility, especially one that is a teaching hospital sine they have more specialists

Good question for you dads doctor don't you think?

It would help if you would fill out your profile and let us know your dad's medical history. What does his doctor say? Obviously something significant has happened and has been happening if he has been struggling to stand up and move more and more this year. I am a healthy 88 year old and have no problems standing up and moving. Your dad must have some underlying health condition. People don't stop being able to move for no reason.