Ouch.
I have a medical condition involving my knees that's still being diagnosed by the 'ever-seeing' doctors. (For the last 10 years)
As noted in a previous (my first ever) post, I also have had a hearing problem since childhood.
It's all related to the carts in my joints, as per the doctors.
I've never had groin pains as a result, though.
I feel for you with the knees.
At times, I can't bend my knees, period. And they sweel up to twice their size. But, I can put all the weight I want on them at any time. It doesn't make sence.
Since I can keep them straight and put weight on them, I still pass for my 3rd class.
It seems that since the pain runs to your groin, I'd say it's more of a muscular problem, rather than a joint failure.
My 'boys' have never been effected and I've had knee problems since I was 14. (I'm now 28)
(I once went down on the ramp because my knee decided to 'split' on me during a fueling)