Gordon's meniscus (fibrocartilage) is fine, so he's clearly having problems with his hyaline cartilage (or articular cartilage), which is what covers the tips of your bones and provides that smooth glide in the knee joint. What hasn't been said is if it's the articular cartilage covering the tip of his femur, tibia or behind his patella (knee cap).
A lot of you fans are uneducated. The cartilage is a tricky material. It's totally avascular, which means it has no blood supply like other organs, which means it takes longer to heal. This is a crucial time for Gordon. IF he does further damage, he could need micro-fracture surgery to create new articular cartilage (the newly created articular cartilage isn't as good as the original though). IF his condition is anything like Andrew Bynum's, it means his articular cartilage is a little soft or in a "weakened state". That's probably where the bruising and swelling came from.
Gordon is doing the right thing. He's strengthening the quad, which is major to the health of his knee joint. He's also giving his knee rest, which is clearly what it needs. I think it's good that he hasn't played on this, making it worse.
It sucks, but it is what it is. People will just have to be patient. He'll come back 100% and avoid any future problems if he stays patient.