Vet Visit

Question
My 7 month old yellow lab has been limping for awhile now. We brought him into the vet about a month ago, and she said he just had a muscle pull. We let him lay low for about a week and he seemed to be getting better. However, the limp started up again. He limps on his back right leg. It looks like when he walks his leg/hips rotates in. I fear that it may be hip displaysia, but he's so young.Also, when I take him to the park, he runs around at full speed perfectly fine, he only seems to limp when he's walking around the house and he doesn't whine in pain. We have another appointment for him to see the vet, but I was just wondering if you had any thoughts as to what might be wrong, maybe just to give us an idea.
Also, he is very wild when he goes to the vet, which makes it difficult to have him examined. I know some people who give their dogs like a sedative that calms them down. Is this something I should look into? I don't want to do it if it may cause health problems. Any information is greatly appreciated!

Answer
If you live in an area where you can see an orthopedic vet, I would see them before going back to your regular vet.  And you WANT xrays to be taken of the knee and hip.  

A couple things could be wrong.  It could be a muscle pull for real.  But sometimes they take a LONG time to heal especially with a young dog.  Resting them means seriously NO ACTIVITY other than potty and resting in a confined area for a few weeks, but typically a month.  

It could be a torn or partially torn cruciate ligament.  An xray won't show this but an ortho vet can do a special test on the joint to see the cruciate is the problem.  

It could be pano.  It's where the bones grow unevenly and cause pain, but it's typically associated with moving lameness where it could show up in all the legs.

It could be Hip Dysplasia.  An xray will show this.  Were the parents OFA certified on their hips?  While this would not preclude the dog coming down with a problem, it helps to know if the parents were tested and what the breeder's policy is on hip problems.  

Yes, the dog will need to be completed sedated for a proper exam.