Walking or stumbling
 

I wonder if anyone has suggestions for the following? Recent knee replacement recovery was going well, until approximately 1 month ago. Surgery was in July 08. Currently when walking or standing for approximately 15 minutes, the muscles in my lower back become numb. The sensation is similar to the focus trying to keep from falling. I know the spine is arthritic, but my posing the question to doctors seems to draw only a "ho hum" response.
Lower back of both legs becomes numb also and it is becoming a real annoyance.

it is possible
 

That your leg was made slightly longer during the replacement.

When that happens, the rest of the muscles/ligaments in your legs/back have to adjust.

I'd get a good chiropractor to check you out. If it turns out that the operated leg has changed, you may be able to fix the problem by putting a lift or shoe orthotic in the other shoe.
A good podiatrist can make those for you.

I have seen knee replacements put on CROOKED...twisted.
Those people have a hard time walking as well.

How are things now?