You must be so frustrated by all this!
My immediate reaction is that you don't really have a solid diagnosis re the original injury and after 8 months there has to be an element of chronic pain here, where at least some of the pain is being generated by your nervous system itself.
To deal with the first issue of diagnosis: I would suggest that what you did was to smack the knee cap into the bone of the joint surfaces behind. (No brainer from your photos and description!)That would give you a classic periostitis which is characterised by an "exquisite" pain - not an ache or a stabbing, but really a pain like no other! This would be on the assumption that you didn't crack the bone of the kneecap. Good way to do it is to whack the knee really hard or fall on it directly! It maybe worth getting an X ray to rule out a fracture, but also to see if there is any calcification under the periosteum (membrane covering the bone and very well supplied with blood and nerves!) If you didn't fracture, then you can get the situation where there is swelling under the periosteum, which in turn can turn into bone - this would show on a plain X ray.
I would expect the physio would have found any ligament damage etc with a full clinical exam. If not then you wouldn't be able to do half of what you are doing with ligament, meniscal damage etc. So I would rule those possibilities out.

The ongoing pain appears to be the real problem and this is either because of damage etc to the periosteum and/or the chronic pain. Simply, pain does not come from damaged tissues. Messages are sent to the brain that something is wrong and the brain decides what to do about it. In the first instance, it will give you pain as a warning that damage has occurred and to make you look after it! Interestingly, if there was a marked danger to you, as a whole, at the time of the injury, that you may fall off the wall because of the pain, then you wouldn't feel anything at that moment. Only when you are in a safe situation will the brain allow you some pain!
The problem is that the pain can persist even after the original injury has long since left the building! It has become almost a learned response. Your brain has learnt that putting the leg under load, or putting pressure on the front of the leg etc etc previously caused trouble. Even though everything is now OK the nervous system has become "nervous" about you getting back to full fitness and activities - so you still feel pain!

As to treatment: If there was no fracture and the periosteum is ok then I would treat the back of the kneecap with Interferential Therapy to make sure that there is no persistent, underlying inflammation. I would still do the same, but different frequencies if there was a fracture/peristeal problem. That gets the "passive" treatment sorted and after 35 years of working with IFT, I can tell you it works!
My personal maxim is "Heat on the body and ice in my gin". It is far too late for ice etc. Get a simple wheatbag if you need to.
The pain issue can be dealt with by thinking along the lines of - I have had an X ray and there is no longer any damage in my knee. Therefore, what I need to do is retrain my nervous, nervous system to realise that pain does not equal harm. ie hundreds of painfree movements in sitting and/or standing. I don't care how you move your knee as long as it is PAINFREE. Range doesn't matter - just get it moving. Don't go and do weights and heavily loaded exercise until you have complete full range, painfree movement. Then gradually increase the loading until you get full fitness back. The old adage of "do 80% of what you think you can do" works well here.
I have had patients in a far worse situation than yours and they recovered fully in a few weeks - BUT you need to get your head in the right place and I would suggest an X ray will allow you to do this by putting your last fears away.
Hope this rather lengthy reply helps, but you should and can be better!