Since you are not a doctor, with no possible credentials, I have a question that I would only ask some homeless guy in the street, so that there are no legal issues.....
A few years ago, a doctor asked me, out of the blue, if I ever lost muscular force in me knees from time to time. At the time, I said no, and wasn't sure where the question was coming from.
In the last 3 weeks it has happened to me 3 times. Complete loss of force and down I go.
As a total amateur with no possible credentials at all, what is your wild ass guess?
I will go see the doctor, next week I hope, but the health system is a mess here.