Apparent weakness in puppy's back legs?

Asked by livelaughlove21 (15724) August 30th, 2013 from iPhone

We have a 9 month old border collie mix. Ever since we got her at 8 weeks old, I’ve noticed her backs legs or hips seem a bit weak. If she’s lying down, she pulls her upper body up with her front legs, but the back legs take a few seconds. I mostly notice this when she’s on a soft surface, like the couch.

HOWEVER, she runs and jumps with no problems. She’ll jump on us to where all of her weight is in her hind legs. They’ve never collapsed under her and they don’t shake or anything. She doesn’t act like she’s in pain and she’s had no injuries. She’s not even a year old, so usual suggestions like arthritis or some degenerative condition seems unlikely. She’s at a normal weight (38 lbs, medium sized dog), but her legs have always been long and skinny.

I haven’t mentioned this to the vet because it hasn’t gotten worse or affected her activities in any major way. Frankly, I never think about it while I’m there. Plus, it would be hard to show the vet because the pup usually acts like a psycho at the vet’s office – jumping around all excited. If I mentioned weak legs, she’d probably look at me like I’m crazy.

This is my first dog, so perhaps this is nothing and I just never noticed it in other dogs before, but I thought I’d see if any of you have seen this.