My 6 month old labX weighs 50 pounds and only goes up to about my knee, the vet at 4 months told us she'd be roughly 90 pounds (her dad was 120), her mom was only 60 pounds, will she grow any taller? She isn't overweight, nice and sleek looking, she eats about 4 1/2 cups of food a day and is very active, we walk 3 km twice a day and play "fetch" in the yard.

At 6 months most of your Labs and Lab crosses have about 90% of their adult size. She isn't going to be a big girl. Switch her to an adult chow if you haven't already. It slows growth, eventually giving you the same size dog, but with sturdier joints. Make the switch over about a week, and stick to the same protean source if you can. Sticking to one protean as long as you can, makes it easier to work around if the dog develops allergies later.

What is she crossed with? Does she look mostly Lab? Many crosses do, but my friends have a Border Collie cross, Lab body except for the BC spots.

Keeping her lean is one of the best things you can do to give her strong joints, and a long, active life. Here is a link that will help, http://www.photolocker.net/images/Labman/proplanc.jpg

Labman, her dad was a 120 pound purebred yellow lab, mom was 1/2 black lab, 1/2 german shephard, she threw 8 black puppies, brina was the largest of the females, up till she was about 4 months, you'd swear she was pure lab, but now her face has slimmed out and she has courser (sp?) hair on her back, her feet are webbed. I switched her to adult food when she was 4 months as the vet/trainers suggested.