This puppy was born with legs bent (curled) inward toward the abdomen. He could not straighten out his legs. They were stiff to try to move manually.

This is the same puppy next to another with normal legs

Daily range of motion exercises quickly helped with mobility and straightening. This is the same puppy about two weeks later:

And the same puppy walking. You can't see his rear legs well in this photo, but they were normal: