Your dog is exhibiting some classic signs of Hip Displasia.
Hip dysplasia is an abnormal formation of the hip socket that, in its
more severe form, can eventually cause crippling lameness and painful
arthritis of the joints. It is a genetic (polygenic) trait that is
affected by environmental factors. It can be found in many animals and
in humans, but is most commonly associated with dogs, and is common in
many dog breeds, particularly the larger breeds.
In dogs, the problem almost always appears by the time the dog is 18
months old. The defect can be anywhere from mild to severely
crippling, and can eventually cause severe osteoarthritis.
It is most common in medium-large pure bred dogs, such as
Newfoundlands, German Shepherd Dogs, Retrievers (such as Labradors,
Tollers, or Goldens), rottweilers and mastiffs, but also occurs in
some smaller breeds such as spaniels and pugs
I have had 2 Pekingese that dealt with hip displasia their entire lives and other than occasionally needing to adjust themselves there was not problem they needed fixed. But in the larger breeds it almost always leads to arthritis which can reduce your dogs quality of life. You should begin talking with your dogs Vet about preventative things you can do to help delay the onset of any debilitating conditions. It could be that your dogs hips are so bad that they may need reconstruction. But that is something you will need to consult with your vet. That said you probably have several years before you need to consider and major options. But for now you should talk with your vet about ways you can help prevent the problems and maybe your dog will be able to avoid these effects altogether.