The term "knee damage" can encompass many different conditions and injuries so let's just examine at some of the more common ones you might be looking at:
Osteoarthritis of the knee is when the cartilage in the joint has become thin or worn and the body is unable to "keep up" with repairs. Walking generally isn't going to cause this unless ...
I'm a physical therapist (PT) - considering we specialize in the application of movement and exercise.
Consistency NOT time of day is the key to any exercise regimen.
A walk in the park at 6AM or 2PM would have the same effects on "health".
Ask him explain to explain the reasoning behind this - and - if he'd send or write down the the name of the research ...
1) Walking can actually help, even in people who already have osteoarthritis.
Daily walking and the risk of incident functional limitation in knee OA: An observational study (Arthritis Care Research, 2014):
Walking over 7 days was objectively measured as steps/day within a
cohort of people with or at risk of knee OA from the Multicenter