Since the beginning of the show, I have wondered about House's injury. Not so much the injury itself but the timing and circumstances of the injury. There are several options that I can think of:
1.) House' s misdiagnosis occurred when he was young and this drove him to be a doctor. This has been shot down by the teaser for "Detox."
2.) House's misdiagnosis occurred while he was a doctor but before he became a diagnostician. Thus causing him to go into the specialty so that the same thing wouldn't happen to others. It would explain his dedication to his specialty (including the specialty of nephrology since muscle death causing protein dumping into the kidneys). However, in the teaser for "Detox" Wilson states that "[he] was there." Unless Wilson and House have known each other for nearly twenty years, this option is also improbable.
3.) House was already a diagnostician, but was misdiagnosed by another doctor. This seems to be the favorite among the fic writers and is the one that I'm voting will become canon. It definitely seems to be the most realistic as it is generally accepted practice that doctors should not treat themselves or close members of their family. However, not only is this not an official rule, the House we see could very believably be too stubborn to let any other doctor treat him. This would also give a great reason as to why House is so angry and has such a low opinion of his peers. (Not that he would ever refer to them as such.)
4.) House was already a diagnostician, and misdiagnosed himself. Being a charter member in the House School of Angst (as Auditrix says), this is my favorite option. Someone mentioned it last month (I wish I could remember where) and it blew my mind. I really like the potential angst and depth to the character it gives. It also gives a real good reason for why House is so relentless and obsessive about finding the cause of any illness. (To the point of tearing apart the dispensary to find the exact gout medicine the boy accidentally received in "Occam's Razor." Option #3 would explain this as well, but I'm ignoring that fact in light of my bias towards this option. (Of course, there's also the problem that this would hint at the possibility that House wasn't as good a diagnostician in the past.)
I'm sure these questions will be answered tomorrow in "Detox," which is why I wanted to write out my thoughts BEFORE it aired.
I'm betting that if they DO say, it will end up being Option 3, but until I hear otherwise, I will pretend it's Option 4.