!!!sorry for the length, but now you can choose what is relevant of my case to you instead of myself choosing................
I have read most people's posts on here and there appears to be a painfully common problem along with a painfully absent solution.
I believe my doctors, after extensive examination, not to mention more or less trial-and-error surgery, had correctly identified the causes of my knee locking. (I will discuss detail further down message)
I have experienced a random locking of my knee (later developing to both knees) since the age of 10 (now 27). Like most, it has occured from varied activities such as running, swimming, sitting, standing, kneeling, rolling over in bed, and any other which way.
I had 3 surgeries (2 one knee, 1 the other) between the ages of 12 and 15, and until one year ago I thought my locking problem had been fixed. 10 years with no problem only to wake up to pee in the middle of night for my knee to lock up for just over 24 hours. (The longest I remember it being locked for was 3 days!
One week ago while playing hockey it felt as though it was about to pop and lock but since then I have experienced extremely limited movability along with the usual pleasantries of pain, but it is not locked. (convincing me further that my doctors were on the right track).
From 1994 (first locking) until 2000 (3rd/final surgery) I had seen many doctors and they had discussed with many colleagues, as this condition was new and perplexing to them. But they honestly told me they didn't know but were doing all they could to learn, and heard from knee specialists across Canada and the US about only a handful of such cases. They eventually arrived at a deductive assumption that a part of my catilage was loose and jamming somewhere in the knee to cause it to lock. The loose cartiage could be removed and voila, the magic of science.
This led to my first surgery, whereup during the surgery(orthoscopic) it was concluded that not a part of my cartiage was loose but the entire thing was popping out and locking up in (what my non-medical mind understood as) a small opening in the tendon which had stretched/ripped/grown large enough for the loose cartilage to snuggle into, causing the entire knee to "lock" and an amount of pain I am sure you others can relate to. (Bruce Willis even could not bear this I am sure).
With the cause of my spastic knee-locking known, my doctors fully assured me that each time it locked, my cartilage was weakening into basically a conglomoration of mush eventually becoming play-doh (not great for the purpose and duties required by anatomy of a cartilage) along with other damge being done to tendons or other doohickeys in there. THIS I BELIEVE IS THE most correct any doctor has come to earning his PHD through work and science and using-of-the-brain instead of earning it by just showing up to class, as just showing up is what it seemed so many unknowing doctors considered their job. DO NOT LET IT KEEP LOCKING. get it fixed asap!!!
With the problem hopefully identified I went in for another surgery (my other knee joined the lock-party only a month before my scheduled surgery, yay!). This time it was open knee surgery, cutting right into the side. They apparently sowed the cartilage secure into place and sewed the hole around the tendon back to it's proper tiny size, so if the cartiage did pop out, it was find no home in the tendon, leaving only it's intended position to rest.
My next surgery (on the other knee now) was the same strategy as the second (seemingly somewhat succesful) surgery although orthoscopic not open knee! I believe my knee (in years recent) has popped out once or twice, but with the cartilage finding no place to park in the tendon, in split second fasion ducked back to it's alloted place in my knee, leaving me with 10 terrifying and somewhat painful seconds before noticing my ability at mobility!
I believe now over time I have re-opened the tendon to the nomadic cartilage and am petrified on it locking up again. Last year when it locked after 10 years without, it was as painful to my spirit as my body, and now it has felt wacky for a whole week but without full locking.
I live in Taiwan now so I will go see a knee specialist here I hope and see what these doctors have to input, but will return to canada in a few days for the summer, so see what happens.
ps...my surgeries were performed in Rossland, BC, Canada.
ps.ps.....black-market knees must exist on some markets, maybe can get a group deal from a generous body pirate if anyone is fed up with their knee.
I hope the auto-biography of my knee has been helpful or insightful. Good luck to us all and to all a good night.