5 month old lab with stiff/ wobbly hind legs

Question
We have a 5 month old female black lab (pointer?) mix pup (adopted a month ago, spayed 10 days ago) who has developed some stiffness/ unsteadiness in both of her hind legs over the previous 2 days.  She's stumbled a few times on walks and around the house, walks more slowly, and is now very reluctant to ascend or descend the 5 or so stairs in our house.  She doesn't appear to be in pain or discomfort, and she'll let us manipulate her hinds legs without any observable distress.  She's been growing by the day and I'm wondering if this might be growing pains (her hind quarters are higher than her front# or something more serious #e.g., hip dysplasia).  She's fed a premium puppy mix and there has otherwise been no apparent change in her appetite or behavior. Again, this all emerged within the last few days.  Thanks for any input.

Answer
Growing pains don't manifest as severely as what you are seeing.  Please get the dog to the vet and have them xray her hips to see what it looks like in there.  You want to see if the dog has signs of hip dysplasia.  If nothing is apparent, another test that might give you some information is the test for EIC or CNM.  You can google those to find out the details.  Of course, these are all worst case scenarios.  But best to rule them out as soon as possible.

Good Luck.