I rode my MTB at work yesterday. There are two sections of conservation land close by that are connected by a 1/2 mile section of double track that is _sort_ of private, but has obviously moderate use. All told, it's 8 miles of decent riding, about 50% single track with a couple hard but short climbs/descents, reasonable amounts of mud (really sloppy in the spring). Much of the single track is reasonable rocky/rooty/twisty....fun at speed.
Also there are about a dozen stone wall crossings. Though most have been 'opened' to make them more ridable, a few still require some significant maneuvering of the bike to pick up the front end, avoid digging in the chainring, then balance the drop with picking up the rear wheel.
Yesterday, I took one of them a bit too fast. This wall only has a slight 'notch' where the trail crosses, and is on a slope. I was crossing in the downhill direction. The front wheel dropped into a slight depression, I was too far forward, the shock bottomed out and I was launched. As I pitched forward head first, my right foot unclipped and my full weight slammed the stem with my right knee, hitting the steerer tube with the connective tissue just above the patellae. I actually saw stars and went light headed (easy there, solo). This picture shows what I looked like after the ride, before getting cleaned up:
Now, I know how to handle this. Unless there's an obvious break, get right back on ASAP....ride out the pain. This worked...except that I noticed I was still in real pain after a few minutes of riding, usually not the case.
My right knee has significant swelling, I'm walking with a limp. Putting lateral strain with weight on the knee sends shooting pains. This picture is from this morning, after a nights sleep:
Notice how my right leg appears to be turned outward...it isn't, that's the mass of swollen tissue on the outside of my right knee. This picture is a right side view of the right knee: