Two questions:

What type of amp did Bree have- was it a mid-femoral (they really only leave a small piece of the femur) so she has a bit of a butt cheek on that side, or did they take the entire femur?

When you say she falls- does she fall to a sit position then fall over, or does she fall from standing?

My first tripawd Maggie was a left rear amp, she had a mid-femoral amp and so had a good base to sit on. When her one leg got tired or she lost her balance she would fall into a sit, I don't remember that she fell all the way down too often unless helped by her sister. While standing her whole body would sway- and sometimes her back leg would wobble.  That's how I knew she was tired.  At first it was difficult for her to stand and eat her food.  As she got stronger she could stand solidly for a long time.

My second tripawd Elly is a right rear amp, her whole leg was removed.  She does not have a good base to sit on. For example- Maggie when sitting could 'shake hands' with either paw and keep her balance.  Elly can only shake with her left front paw, and only if her remaining left rear leg is positioned correctly.  I hope that makes sense.

I've had Elly for 3 months now, she is more than 5 months post op.  She didn't get any therapy or much walking time while in foster.  She did play a lot which I think worked in her favor.  I started her immediately on core exercises, some of which are games for her, and slowly started her on short walks.  She is much stronger now than when I got her, but certain things are still very tiring for her.

One I just learned is standing, mostly still, for long periods.  I recently started her in a small dog obedience class, it is one hour once a week.  Because she is a bit uncomfortable around other dogs and people, and because she doesn't like the floor she stood for the entire first class.  She was really tired after that!  I think it takes way more energy for a tripawd to stand still or walk slowly- they are most efficient at a sort of gallop. I now take a small rug that she likes to class.  This was 5 months post op, and 3 months after I adopted her.

So I'm thinking that Bree has maybe been standing more than she was before? Even a small increase in activity for a new tripawd is very tiring.  I highly recommend going to a rehab vet or getting started yourself with the information available here.  I'm still learning how to gauge Elly's activity levels and make sure she doesn't over do on one activity or the other.

This got kind of long- hope it helps a little.

Karen and the Spirit Pug Girls