This is partially just sharing and partially a question.
Alvin has been limping for about two weeks, following a bad dismount from my very-low-to-the-ground car. I assumed he had pulled something and so I waited for a week to see if it would go away. It didn't, so I scheduled a vet visit, which happened this afternoon.
As it turns out, he has a partially torn anterior cruciate ligament. That would be a bad knee, in layman's terms.

The vet said dogs with heavy builds like Alvin's are prone to this particular type of injury because their legs are essentially too spindly for their big, burly bodies. It's actually the same kind of injury football players get and for the same reason.
At any rate, it's a pretty serious condition to have, because ligaments do not heal themselves like muscles. Scar tissue will form, but it will take a while. Alvin is not allowed to do anything but go outside to pee for a MONTH. After that, he is allowed to shuffle a few houses down the block for a month, then possibly around the block for another month, until we can work back up to longer walks. They will never be as long or as brisk as they used to be, however. The vet said that if he should ever have an accident where he slips, falls, and completely tears that knee, that we could end up with a three legged dog.
Yikes.
Anyone have a recommendation for a good dog ramp that we can use to get him in and out of the car safely? There are a lot of options online...does it really matter which one I get?