Try to do stretching, yoga, etc more than once a day - many smaller 5-10 minute sessions are as beneficial as one longer one, and probably more so if you tend to sit a lot. As for knee/leg pain, can you pedal a bicycle? A stationery bike with adjustable tension is a great option - it doesn't need to be big & fancy with a lot of electronics. And start SMALL - baby steps - when I started pain therapy last summer, I was given one new exercise weekly to add to my regimen - sometimes only 5 reps. The same after hand surgery - one new task at a time over 8 weeks...
Now I have a series of stretches I do before I even get out of bed, more with morning coffee & in the shower, and 3 times a week resistance bands (bad arthritis - weights are not an option.)
Sue