Accepted Answer

The problem of giving away of knee are generally due to either muscle weakness or due to injury to or problem with ACL ligament of the knee.
I do want to state here that there are some inconclusive evidences which shows that in last trimester of pregnency there is loosening of the ligaments like in the sacroiliac joint which occurs in response to give more room for the fetus,this may also be a case with the ACL which is giving you such feeling.
   Secondly due to enlarged abdomen to maintain the center of gravity the hamstring muscles at the back of thigh used to contract more or work more then the normal this may be the cause for your knee pain on the posterior aspect.
   on the safe aspect i will advice you to not to have any medication at present for this ailment,you may use knee brace made from good material to support your knee & keep a pillow under your knee to keep your muscles on the posterior aspect in relax position.A mild sport massage will also help you.
I think it will be beneficial for you.
Wishing for a great future for you & your coming child.
Regards.

Expert:	DR.MUKESH TIWARI ,M.S.
Pos. Feedback:	96.9 %
Accepts:
Answered:	11/23/2008

Orthopaedic surge&on

15 years experiene,trauma surgeon,Qualified women,pediatric &general orthopedic expert .