I have. I blew out my ACL/MCL/cartilage in my right knee (they call it the "unholy trinity") in jiujitsu training in Sep 03 when I was supposed to ship to PLC Seniors second session 04. I was able to get it rehabilitated and graduate from Seniors on schedule. I don't know if you're asking this question just out of interest or whether you've recently gotten injured. If the latter is the case, here are some points of advice.
1) Be honest with your OSO/the Corps. If they catch you lying about your medical history they will put you in a hurt locker.
2) Be honest with yourself and your capability to rehabilitate and carry on training. In my case, I got the surgery waivered and was cleared good to go prior to shipping to OCS for the second time. Luckily I made it through. If I had reinjured my knee in training at OCS, it would have been very tough, maybe impossible, to get a second waiver. My point is, if you get injured, look at the big picture and the goal of becoming an officer, not staying in the particular program you're in. You may have to do more training (ie go to OCC after already having done a summer of Juniors) but it will be worth it in the long run if you need time to recuperate post injury.
3) Keep a positive attitude. After the knee surgery my thigh shrunk to the size of one of my arms. Literally. It was both gross and depressing. Do whatever you can to maintain a PMA and stay motivated, especially when it comes to physical therapy.
Hope this helps.