You are describing "valgus", and this may be a problem if there is premature bone closure of the growth plate. I see a fair bit of odd conformation in puppies that ultimately doesn't affect gait or activity.
The back leg scratching is not a cause. Certainly consult with a veterinarian, and consider slowing down the rate of growth in your puppy with appropriate diet (I advise a good quality adult ration) at the three to four month age, and also avoiding orthopedic stressors such as excessive torque on the limbs.
An example would be young boys who attempt to pitch baseball like their big-league heroes; puppies likewise should avoid extremes in training until more developed.
X-ray films can quickly tell if premature growth plate closure is the cause of this presentation. If not, then time and common sense will take its course. You may not have a show dog with excellent conformation, but certainly an affectionate companion.
Dr. Van Lienden
Dr. Raymond Van Lienden DVM
The Animal Clinic of Clifton
12702 Chapel Road, Clifton
Virginia, U.S.A. 20124