Take your time Sandpiper.
Important to have good running shoes. I'm not sure it orthotics would help here. But to at least walk on softer ground.

Perhaps some form of swimming, if you do swim.

As other forumites know here, I cycle. Many men and women take up cycling in their mid-years and onward. On a properly fitted bike on you, cycling is actually easier on the knees. Many injured joggers, take cycling to save their knees because the sport places less bodyweight on the knees...and you go even farther..

above all, do the type of exercise that makes your heart sing...that's a guarantee you'll keep doing it more often.
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