I'm actually quite agile on mine, but I have got my other leg to help maintain stability and I still have my knee on prosthetic side. Above the knee amputees have it much worse and bilateral (both legs) even worse. I'm the best case scenario amputee lol.
You couldn't really just strap one on, they are each made uniquely to fit it's person. The socket of the leg is formed around the shape of one's stump. They can either be held on by vacuum (highest performance), suction, or like mine - pin lock, which is kinda mid grade performance. I roll a thick silicon liner on my nub, that's about 12" long and goes up past my knee, and it has a steel cup sewn in the end of it with a notched pin sticking out the end. When I step down into my prosthesis, it has a ratcheting mechanism the pin goes down in and locks, until I press the lock release button and it just slides right of. Not as high performance as some, but it's primitive in maintenance compared to the other types. I had an elevated vaccum leg and it was a lot to keep up with, had a remote fob to keep up with to set the vacuum psi, and had to charge the li ion battery every night. Even more trouble going on trips, keeping up with that damn fob and the charger. I had a vaccum related injury one time with it and ended up opting for the more simple pin lock system. It works just fine for me.
