Does pedaling while standing damage my knees even if I don't feel pain? I am in my mid forties and ride a seven speed cruiser or maybe mountain bike. I enjoy pedaling while standing, and I don't really care about speed or efficiency. When there is even the slightest uphill grade and I stand. I get in a high gear and enjoy slowly swaying back and forth and using my arms. I've never really measured my cadence, but I'm sure it is sub 60.

I am putting some longer rides in reasonably hilly country with smooth roads. My knees don't ache afterward. Sometimes my shoulders ache a bit after the ride but doesn't feel damaging. I have been doing hills/grades in top gear as my own "check off the list" challenge.

If proper form (for standing at least) and in good shape, am I abusing my body/knees?  Up to now they feel great, but I would hate to have "reality" crashing upon my knees someday.
Standing to pedal won't damage your knees. Supporting and propelling you when you are standing is exactly what knees are designed to do.

If anything standing is better for your knees than sitting. When you are sitting down their motion is limited because the top and bottoms of your legs are 'fixed' in position. When you stand your knees and hips can move freely which is a more natural movement. Watch a child riding a bike and you'll notice they naturally spend a lot of time standing up.

Standing pedalling does require more core and upper body strength than seated pedalling and maybe that's why your shoulders are aching check out BikeJames.com if you are interested in exercises help with that.

As an aside standing pedalling is less efficient than seated pedalling but it lets you put out more power. If you compare top level riders in pretty much any form of competitive cycling you'll see that they spend a lot more time standing up than a comparable recreational rider.