Since I'm married to Houdini reincarnate

[whippedcream]

The bad knees is a bit of a restriction, but have you tried a spreader bar?

They can be expensive, but this works and is really cheap and easy:

Get about 3 feet of PVC pipe
Get about 7-ish feet of chain
Get a padlock
To be nice, grab the fuzzy sheaths off a pair of furry handcuffs or find some other cushiony soft material.

First thread the two fuzzy sheaths onto the chain if you're going to be nice. Thread the chain doubled through the pipe (Paint illustration below; my digital camera crapped out recently. Have him stick his foot through the one loop, pull the whole contraption tight, and padlock the chain on the other end.

Voila, he's bound and accessible. You can bend him over a convenient-heighted table and tie his arms to the table legs. That should hold the squirmy bugger! Good luck.