The joint problems can show up at any age, since many are caused by genetic predisposition. It is not at all uncommon to see them at ages as early as 2-4 years. There are foods that include supplements for joint health, and there are also separate supplements. The vet visit is the first thing to do, a thorough exam is a good idea anyway.
I just lost my Rottweiler, Gretchen, last month, she was 11. We thought she had beaten hemangiosarcoma and the odds (they took her spleen and a cancerous tumor that filled a gallon bucket, and she was up and around 1/2 an hour later) but evidently complications (an embolism) took her from me a month later. I still tear up at times, and still blame myself for not doing more. They are never with us long enough.