Sorry to hear about your pain, Crazylegs2019. I’ve been in similar situations myself. Sometimes I have been able to run the marathon, and sometimes I had to let it go, along with all the training and expense. It’s a real downer sometimes, but the wisdom of running the event depends on the situation.
In your case, both diagnoses could be correct, in that you may have a knee condition that running can worsen, but you may also be able to compete anyway without doing any damage. It depends on a few factors, and on how you approach this going forward. Having seen a lot of real injuries, and also a lot of pain syndromes, I just want to add that the problem with the knee pain may not be the knee itself. Let’s hope for the best!
A couple things stood out from your lengthy report, that are worth highlighting. You mentioned that after some time off for sickness, you did a 20-miler to get back on track. The other thing is that you can run up steps without the pain.
You’ve probably heard that it’s not a good idea to try to make up for lost training. I’ve tried this too. Sometimes you can pull it off, and some times it will set you back by creating an injury or pain problem. Without writing a book here, I want to differentiate between pain and injury. Doctors are trained to look for signs of real physical injury as the cause of pain. It’s what they get paid for. I trust that the last diagnosis was good, and that the knee itself is intact. It is still possible though, to create a soft tissue problem that doesn’t show up in an exam. The good news is that many soft tissue pain syndromes, if they do not result from actual injury, can be taken care of in a fairly short amount of time.
The bad news is that soft tissue injuries or pain syndromes can alter your bio-mechanics enough to create conditions under which an actual physical injury to your knee can occur. The muscles of your back, hips, legs, and feet must work in concert to minimize stress on the joints. A mere pain syndrome can cause enough imbalance in how the muscles are acting on the joints, that the joints themselves are in jeopardy. This is where you might be, and what you want to avoid in competition or heavy training.
Research has shown that running can actually be beneficial to the knee joints, when not done to excess, or done when the soft tissue (muscles and other fascia) is not functioning properly. One thing to keep in mind is that pain can alter the way muscles work together, so that some are working too hard, and others are working poorly. There are several muscles in the thigh that pull on the kneecap that have to be in balance. Rotation of the hip is also important, in that it changes the angle at which the knee bears weight, and can affect the point in the gait cycle when the muscles and joints load and unload.
In other words, there may have been times in your training when some muscles were pulling too much and others too little, causing possible irritation of the joint, but also pain in the overloaded muscles. The neural pathways that carry this pain can be misinterpreted by the brain as knee pain. This is why the doctor can be absolutely correct about your knees, but you may still hurt when you do certain things.
Another thing I noticed is that you said sitting at the table was painful. This could indicate some problems with hip rotator muscles, which are deep within the gluteal area you are sitting on. Problems here can radiate down the legs and create knee pain by altering the way your legs move when running. Going up steps uses the muscles differently.
You might want to ask if your ortho can recommend a good physical therapist familiar with sports injuries. Many PTs specialize in post-op, but you want one that has worked closely with active athletes. The solution may be as simple as targeted massage, or as time consuming as retraining some under-performing muscles, but it should start with a treadmill exam to see how you are running now. A good PT can spot the problem and design an effective program quickly.
I often suggest a few things to try before scheduling appointments, but you are running out of time to experiment. In this case I recommend booking a session with a good sports PT as soon as possible. It may not be too late!
Good luck with your recovery, and best of health!