I'd have them put pup on Glucosamine/chondroitin WITH MSM and Vitamin C asap. I've had so many similar issues over the years, all resolved with supplement. Last one was the biggest scare - vet said pup had OCD of hock and hip dysplasia and wanted to do extensive surgery right away. Pup stopped limping after a week of the supplement (probably due to the MSM) Michigan State University Vet school looked at x-rays as said "normal healthy pup". My vet then took xrays to send to OFA last week - vet thinks hips will rate excellent (prelim). Pups can tear and injure so easily - mine all now receive the supplement as a preventative. It could be pano, ligament tear, etc., etc. Supplement and crate rest for 2-3 weeks, most likely all will be well and pup will be fine.
Vets are going nuts about x-raying and surgery. I found two weeks ago as I boarded another one of mine that their pup had a limp for a week a year ago. They looked at the info I sent home and supplemented. Pup was fine after a week and still doing great. Their vet was talking surgery also without any x-ray proof and after only 1 week limp. The vets are going nuts - we need to educate our pup families to prevent pups from unneeded surgery and suffering.