Birdie, it seems that you are looking for answers, as we all are. However, very often the best we can do is develop some "working theories." From what you're describing, you have acceptable bend that probably will improve by 10 or 20 degrees as the swelling abates and your muscles get more with the program.
Let me re-state something that I think I relayed previously: I do not know if you have/had arthrofibrosis or not, but if that has been the case, there are a couple of things that go with that. One is synovial thickening with effusion. This causes a host of restrictive sensations. I know, because I've had them continuously for two years. At the end of the day when my effusion is worst and I'm tired, I take the stairs one at a time again. Effusion and synovial thickening also inhibits bend. TWO, the effusion can result in this thing we discussed in my thread called "arthrogenic muscle inhibition." This might explain why your leg is able to bend but does so hesitantly. Why don't you look up this condition and see if it fits?
I have been referred to a "physiatrist," which is a doctor specializing in physical rehabilitation medicine. I haven't been yet. But if you have insurance that covers, you might consider getting a similar referral.