When your practice is about a quality of mind and motion, rather than about particular motions, every moment becomes an opportunity to apply it and to hone your skills, and this is never more true than when one's body isn't functioning normally.
As one ages, one discovers how easy it can be to handicap oneself. An afternoon of immoderate exertion is all too likely to be followed by days of pain and weeks of tenderness.
While avoiding this in the first place is preferable, the need to favor an ankle, knee, or hip can be an interesting, useful experience, putting a fine point on issues of balance, kinetics, and inconvenient neurological responses to pain, like when your leg suddenly decides to go limp and collapse beneath you.
Avoiding too much stress on the better leg is an important part of this process, just as important as avoiding further strain to the leg causing trouble.
But you needn't wait for an injury to put this principle to work. The first step is to pay attention to what your body is telling you. If you feel cramped, you probably need to readjust your position, perhaps expand your lungs. If you feel fidgety, you probably need to move. If you can't get up and stretch try rocking from side to side or front to back.
Pay attention to posture and body mechanics, especially when doing something unfamiliar or lifting more weight than usual, and don't be afraid to ask for help if that weight is more than you should be attempting to lift by yourself. There's no shame in having limits; it goes with being human.
On the other hand, don't be afraid to cautiously explore those limits. You may be surprised how much latitude they afford, even in your later years.