I can understand your frustration, but I feel this is a time to relax and take the attention within.
Cyst like this usually has a course. What I would like you to do is reflect on any injuries or incidents that may have over strained your knee and take your awareness into that area and consciously breathe loving warm supportive thoughts into the area of your knee.
Your body is a hologram of your thoughts about it. If you constantly tell, your body there is a problem, then, that is how it will show up. If you take the time to relax and breathe loving supportive thoughts into that region and visualise all the muscles, bones and cartilages all relaxed and at peace and harmony with each other. The bodies own repair mechanism will bring healing into that region.
You ask "Why is it KILLING me??" I feel it may be the other way round Why are you killing your knee? This is all about self-love and healing. I feel there is a need for you to become more aware of your body and the muscles.
I feel if you joined a Yoga class and learned to breathe awareness into your body as you do the gentle stretching you would increase the flexibility of your body and at the same time become more aware.
You may start to become aware of your body at a cellular level, at a molecular level and at an atomic level. You may start to be able to visualise the different aura of energy associated with each level. You may become aware of what the cause is of the problem and how to change your lifestyle to effect healing and repair.
You need to start listening to the inner voice within and honour your intuition and self-knowledge.
I feel you are quite hard on your body. You need to learn self-love and nurturing and become more aware.
You may find the Energy Balancing Guided Meditation helpful on my web site. http://www.healergeorge.com
Just click on the triangular jelly button to start the recording from the home page.

for a water cyst in my throat, I took vit B 12 shots on sunday and b-12 pills the rest of the week size 1000. it kept my cyst under control. I then went to oil pulling and do not take shots anymore or pills, it felt like after a month of oil pulling that a pair of sissors just clipped it off. good luck to you. If i were you I would do the oil pulling or swishing.