My youngest dog always walks around the house and back yard like he's ancient. Like, wobbling along like he's in pain, kinda limping. But, when we're on a walk or he's off-lead in the forest, he's like a rocket, absolutely full-tilt 100% of the time, not a care in the world, no think just run. No trace of a limp, seemingly no problems.
I think he's just really lazy when he's somewhere boring? Like a sullen teenager ambling through the halls at school.