I agree with GamingGrrl.
It's your life, not his. You enjoy riding, stand up for what you enjoy.
Both riding AND running are hard on your knees. My knees at 24 are trashed from years and years of riding. Doesn't help a four year old mare broke my knee a couple years ago, but it can be strenuous on your body.
'Course I'm a thick rider, so I'm sure between walking with my weight and riding, hastens the trauma to my knees. Regardless, both will wear/tear down your knees eventually.
Rhett | Fiona | Rockstar | Remington | Sierra | Savannah | Coal | Magic
TWH Gelding | IDH Cross Mare | SSH Gelding | Mini Yearling Gelding | Mini Driver | Mini Project | My Pony Trail Drive | The Rescue