I am in line for a knee replacement, and went to the tadpole bent this spring. Knees hurt when I walk, but not when I ride. These machines have gears for hills, and go-fast gears. I like my Cat 700.
Will not go back to a DF bike.
Rode a Metric yesterday, second one this week. On the last 20 mile stretch to the barn, dropped a much younger rider on a Felt DF with good kit. Dropped him ON A HILL. Never saw him after that. LOL
Put the trike in SCAT mode, knees did not hurt last night, feel great today.
Learn to spin and it's all good.