Drake is just over 8 years old. They get stiff for sure after 6/7 yrs old.
It is sad when they get older and start to feel the years. It is OK though...remember that, it is all part of aging. Life's activities (including food consumption) should be adjusted accordingly.
Simple things too. I don't command drake to sit anymore. He knows his manners and what matters is if I need him to sit he will and that's good enough for me.
I have a long fast paced walk with Ava that drains her obnoxious energy. Drake stays home for that.
Then I have a walk with drake and Ava where we walk at drakes pace (and Ava runs around like a lunatic) and he lets me know when he wants to go home. Drakes walk is still a good 45/60 minute walk each day, it's just on his terms. So around the same spot of returning, we just turn around and head home. It is important to have exercise every day to keep things moving, but impact isn't exercise. I have a ramp for both of them to use when getting in and out of crates in the back of the truck. No jumping for either of them.
I can not stress enough the amazing properties of Sasha's blend.
Admittedly it's not Drakes favourite but I mix in his raw organs and a raw eggs and he doesn't even notice.
Another thing to consider is the food being consumed. Wheat, soy, preservatives are all inflammation inducers. Raw chicken provides a lot of glucosamine and so many beneficial nutrients that are decreased or slaughtered in the kibble process.
Cinder blew both her ACL's. when she had just one blown she wore a custom orthodic brace. Expensive but what a difference. For her she also got a heating blanket under a blanket on her bed and an ice pack on the other end that I refreshed throughout the day. She figured out which one she wanted and would sit on them accordingly. (Usually the heating pad). But the option was hers. She also had Sasha blend.
Ava also gets Sasha's blend for her rapidly growing joints!
I don't know if you want all that info and my opinions/experiences, but there it is haha!
Drake is a golden retriever (shaved for the summers so his fur is still growing back in).
Just keep on loving, sounds to me like you're doing great and your lab has a fantastic home!
she's getting big. She has a very very playful personality and is such a sweetie. 
