Continued knee problems after surgery

In 2003, I had a tib-fib fracture, which resulted in the installation of a plate and 7 screws.  I did not have any problems after the surgery with this area.

In Jan, 2008, I felt and heard a pop in my knee, just above where the hardware was installed.  Several hours later, my knee swelled to a point of barely being able to bend my knee at all.  I also had great pain in my knee area, especially on the inside of the knee.

My doctor had me do PT 3 times a week for two weeks with no result.  My doctor tried a steroid shot in my lower inside knee and my knee swelled more and I had increased pain.  

I had surgery in Feb 2008.  The surgeon removed all hardware and said he patched a hole in my cartlidge and two holes in my meniscus.  I began range of motion and weight bearing PT 3 times a week and have been do so ever since.  

It is Aug 2008 and I still have swelling (average 2 cm) and significant pain.  

Any ideas of what could be causing my swelling, pain, lack of improvement?