The pup is 10 months old.
Since he was bought from a petshop you are very lucky that things are not worse.
There are all sorts of things that can be done to help him with his elbow and hips. Do a google search on "canine hip dysplasia"...there is a ton of information on how to help this condition with diet, supplement, and certain exercise. Also do a search here...many of us have/had dogs that had HD.
I would get him on glucosamine/chondroitin ASAP, as well as salmon oil and MSM, keep him on the slim side and feed him the best food (more quality meat,etc). Also do not do any long stretches of running or jumping...shorter more frequent amounts are better....swimming is great.
Gina