Sorry to hear Brock is limping!
We had a similar issue with our dog Mac. We re-homed Mac 6 years ago from an owner that never addressed his poor joints and hips. To this day we are still not sure of his age but he is getting on. We have used a product that has made a dramatic improvement to his muscle develop around his joints and also lubricated them for better movement. He has kicked his limp altogether and the only signs of fatigue we see are after long days and we think that is due to his age.
We loved the product so much we now have a website that sells it. I'm not here to make a sale in any way! I simply want to help if I can.
If you are interested PM me.
Hope Brock is feeling better.
Feel free to have a look at our canine health supplement site - kingly-pet.com