Teddahlia True that, about knees. I had a doctor tell me decades ago after x rays that my knees looked like "swiss cheese." I bruised my patella badly at 40. was told never to kneel again. Ha ha. Yeah, right, doc. I use kneeling pads when I have to and i don't mind dragging them around. They're light and if you have a few, they're handy for more than gardening.
I still have both knees at 72, so i must be doing something right. The hips on the other hand...
So is gardening a pleasure and good exercise?
All that grunting and groaning and tugging keeps my vocal cords in good health, as does swearing - which keeps my vocabulary spicy, and I don't use buzzwords like 'smart' this or that. and lose all those good expletives.
Getting into contortionist positions is a lot of fun, and works muscles I would never voluntarily work at, say, a gym - or weight lifting.
Most of all it helps my mental health, being alone. I talk to birds, bugs, plants, frogs, bumblebees, butterflies. I'm never lonely. They don't give me much sass either. My olfactory sense loves all the smells of the garden, my eyes are delighted by color and form, my ears love the hum of bumblebees, - it's good for my entire soul.
Digging up tuber clumps in sticky clay mud on the other hand... not so fun. Sure glad I dig every year. How do people lift those tangled messes of 40 lb clumps? Dividing those is torture, and you don't end up with more than if you just dug the durned things.