Re: unusual seiza problem - pain in BACK of knee
I also know people who bought into semi-permanent injuries by gritting it out. Knees and shoulders are not joints to screw with.
For the OP, I totally wouldn't trust any internet diagnosis. I'd just advise not doing things that hurt more than you can help (so seiza to bow in and out but not otherwise unless you must) and work with people who are there with you on what the real problem is.