Some dogs get over things more quickly than others.  Pumba had no interest in going fo walks for a long time.  Dog park good - aimless walking bad.  Now he loves to go and most days will do the dog mind trick - staring until we get it and take him out.  It's hard to believe it's been a year since he had his front leg removed.  We were very luck that the os had not progressed to his lungs.  We don't take the old long walks anymore.  I read that dogs put 60% of their weight on their front legs.  Pumba was 173 lbs pre surgery and is now down to a svelt 150. He tires quickly - but the stress must be verrrry tiring.  We give him low dose tramadyl for pain when he overdoes the walking and he usually rebounds well.  May I suggest that you try to keep your big fella on the grass?  Concrete is so much harder on the leg/shoulder.  Also, if you can bring him to a place visited be other dogs, his nose will become engaged and he can work through issues better.  We also keep him w/in sight of roadways in case we have to go get the car and "rescue" him.

Wish you luck in the years to come with him - you're past the hardest post surgery phase and just have the enjoying eachother's company to go.

Do you know why I am seriouslab?  One day (before the stupid OS came to visit) we were walking and a man who was walking his labs looked over and said "Now that's a serious lab"  my favorite description ever.  Pumba is a quadruple mixed breed with the look of a giant black lab.