What Causes Pain And Swelling In Knee After Deep Laceration?

I fell directly on my knee (the knee was bent) on a ceramic tile floor. I had a laceration on my knee that was closed with 6 stitches. My knee still swells during the day and is painful when I can finally get off of it and rest it. I am having trouble bending it. The pain seems to be mostly on the left upper side of my knee. The laceration was deep (i.e. I could see ligaments/tendons). Could something else be wrong besides just a laceration? X-Ray shows nothing is broken.