Stairs are one of the first everyday things that get harder as a dog's joints age — the repeated bending and weight-bearing on the way up, and the impact on the way down, ask a lot of a stiff hip or elbow. Here's what actually helps, beyond just "be careful."
Give them a warm-up before the hard climbs
Joints move more easily once a dog has been up and moving for a few minutes. If you can, let them potter around the yard or take a short easy walk before asking them to tackle stairs, rather than the first thing after a long sleep.
Watch the flooring, not just the stairs themselves
A dog with weak or painful joints often struggles more with the slick floor at the top or bottom of a staircase than the stairs themselves — that moment of losing traction is what causes the real hesitation. A textured runner, rug, or grip pads at both ends of the stairway often helps more than anything about the stairs.
Don't force the full flight if there's an alternative
If the stairs in question lead to a bed, a car, or a couch rather than being unavoidable (like the only way to the yard), a ramp or a set of shorter, wider pet steps genuinely reduces the joint stress of that specific climb — several smaller, gentler steps ask less of a stiff joint than a few big ones.
Support their back end on the stairs that can't be avoided
For stairs a dog does have to use, a rear-support harness with a handle lets you take some of their weight on the way up without wrestling with them — most dogs adjust to it quickly once they realize it makes the climb easier, not harder.
Know when it's more than "just stiff"
If a dog is refusing stairs entirely, crying out, or the change happened suddenly rather than gradually, that's worth a vet visit before anything else — sudden changes point to something more specific than general age-related stiffness.