Knee Injury

About 9 weeks ago I was carrying a heavy log (50 lbs)and fell. While my foot was planted to the ground by the weight of the log I fell backwards and had to twist to the left to keep the log from landing on me. My knee was bent all the way back. It was very painful. I have not sought medical attention. I have most of the use of my knee back (95%)except I can not straighten it all the way and lock it nor can I bend it all the way back. The knee feel thick or slightly swollen when walking up or down stairs