Well, my first thought was that you could find someone whose electrically-powered hydraulic pumps had failed and offer to help out by working their hand-operated backup pump for them. But, after some reflection, that seemed silly - especially as the only places I know have hand-operated backup hydraulic pumps are submarines, and clambering up and down submarine ladders would be tricky with your balky knee.

So I guess I'd just have to suggest lots of swimming.