My wife is a utility cyclist, cycling for errands at least 4-5 times per week and up to 3 trips per day, but usually under a few miles per ride. Often she has to carry a heavy load (rides a tandem with trailercycle and two kids and four panniers), bringing the kids to and from school, riding on some hilly streets. So, she rides very short rides but has to pedal very hard for those short intervals. She rarely rides recreationally and never for any distance greater than 5 miles.
She complains of knee pain that she says correlates to bike use. Her knee never hurts when riding, but afterward, when climbing or descending stairs, or just walking. If she takes a week long break from cycling, her knee stops hurting. When she resumes cycling, the pain returns. Again, never while cycling, only when doing other activities.
Is the cycling causing the pain? If so, what can she do (in terms of alternative/supplemental exercises) to decrease the pain? Is it a question of not having enough muscle training? Or is it something else?
In terms of her riding technique, she uses as low a gear as possible when climbing (the tandem has mtb gearing, and her bike has a Shimano 8-speed IGH), so she tries to maximize 'spinning' when she can using low gears, as opposed to mashing in higher gears. The cranks on both bikes are 170mm and she has long legs, riding a 58cm frame. Could shorter cranks be a solution?