Yes, yes, yes! My hyper-extended right knee eventually started malfunctioning in a big way. I'd been using an FES device successfully, but the hyper-extension had been going on since diagnosis i.e. 12 years. My physio told me that the knee degeneration was entirely to be expected and - this was the killer blow - I needed a knee replacement, but if I had one, it would very likely worsen the MS on a permanent basis. This was because during the recuperation period, muscles would weaken through lack of use. For around six months, I had the knee strapped by the physio every week and that relieved the pain. Then the same physio offered to come with me to my FES appointment: she had a talk with my physio there and between them they came to the conclusion that the only option was an orthotic. One was produced for me to try and it was transformational. It removed the pain, encouraged the knee to move normally and sorted the dropped foot. I've often posted about this device, because it's quite recent and not many clinics (apparently) have heard of it. It's called Dynamic Walk, made by Fillauer. I got mine on the NHS, but the full price is around £300 so not ridiculous if you can't get it funded. If you look it up on google and YouTube, you'll see how it works. It's carbon steel, weightless, with a spring that pushes the knee into the right position and a cushioned support for the back of the calf. I have the double-sprung model but depending on how bad your leg is, you might get away with the single sprung one. It has at least doubled my walking ability.

Is this what you meant @cameron: http://fillauer.com/Orthotics/Dynamic-Walk.html ? My knee 'collapses' on me sometimes....is that the same thing as hyper extension?.....on my left leg, the one that doesn't 'do as it's told'. And @perl2: sounds like useful advice from @cameron - hope it helps you. I'm PP as well so if that's my problem too it could help me also.