Hi,
Are you still doing PT? Your quad muscles are still weak. I can do leg lifts lying down, but I have to rest after 10, then do 10, then do another 10. It's not easy. You just need to keep strengthening the quad muscles. Be sure to contract your quad muscle before doing the lift by flexing your foot forward and then your knee will be flat and then try raising your leg. This way you are totally using the quad muscle. Also, is your non-operative knee bent.... That makes it easier for me. And, the above is how my PT told me to do the lifts, and remember, you are only lifting to the height of the other knee when it is flexed. I started out using a strap around my leg to lift it. Believe me, it isn't easy, but it will come.
Everyone heals at their own rate. The muscles take a while to get back into shape, especially if you were not using them much before the surgery. I wasn't and couldn't believe how weak I was when they asked me to do a leg lift at 4 weeks postop.
Hang in there... it will come
Elaine Y.
RBHR -- 1/22/08 -- Dr. Eugene Lopez