Right knee: Lowside impact on bicycle. Couldn't walk for a week. Knee the size of a watermelon. Lingering issues, but it's manageable two decades later.

Left knee: Lowside M/C crash. No impact, but the torque of having my foot under the bike broke the laces (about 300# test) on my 10" Danner combat boots and went right up to my knee. The connective tissue has never been the same since (three years).

In both cases, I've very sensitive to cleat/pedal interface, take Glucosimine, and anticipate a hellish old age. Lots 'o snap, crackle, and pop. And economy class long haul flights are a whole new slice of hell. Get the aisle seat.