Knee giving way more as I exercise more

I am a 49 year old female.  I had both patella removed about 25 years ago (chondromalacia) and in June 2009 had total knee replacement (left knee).  Recovery was very slow (this was 7th surgery on knee and muscles very weak).  I now have 9 degree bend.  Have been doing all the exercises and attending a gym (under supervision) 3 times a week to cycle, do resistance exercises and swim.

I have had pain since the surgery but ths has worsened in the last month.  The knee started giving way about two months after surgery and now gives way 4-5 times a day - this frequency has increased as I have exercised more which I cannot understand!  During the surgery both cruciate ligaments were removed.  Any explanations or suggestions would be welcome!  I regularly use ice and am taking full dose of pain relief medication.  I also have RA - other knee and hips affected as well as ankles and hands etc!

[Abhijeet Ghosh]

Dear Friend,
Well 7 times surgery is really too much.
You are a strong person who has managed well as the knee muscles become very weak after so much operative maneuvering being performed on them.

Don't worry about the cruciate being removed as out knee replacement prosthesis are already having "Cam" mechanism, which acts as "Cruciate substituting" prosthesis.
90% of the doctor's use them only. So for a re-confirmation, you can have a talk with your doctor, about the type of implant being used.
Regarding the "Give Way" feeling, i would request you to meet your concerned doctor and discuss the same. X-Rays and physical examination needs to be done to know the reason.
However, i would also want you to have a second opinion with another doctor, to cross-verify the things.
Meanwhile you can start using a Knee Brace, so as to give you additional support, for the "Give Away" feeling.
Feel free to discuss more, for any doubts.

Regards...