this is a condition called Valgus deformity, it is caused by stress, poor feeding, and too much play on a young pup. luckily, the cure is, lots of good food and crate rest for about 3 weeks, no heavy exersise. we must remember, large dogs have major growth spurts, and need to be careful when they are just babies.
please let any new puppy people know about this. we all know how excited people are about a new pup, and do not realise how much rest a 8 week old needs and lots of good nutrition.. before and after photos in just 3 weeks