Ok, thank you...
First, tarlov cysts are fluid filled sacs that are found (usually incidentally, meaning they usually don't cause symptoms) at the bottom of the spine.
These fluid filled sacs can, occasionally, put pressure on the nerves, however. If this happens, it can cause radiating pain down the leg. It appears that your cysts were not pressing on the nerves since your study was deemed normal...
Arthritis in the knee can, in some cases, be quite severe. But, without morning stiffness, this makes arthritis less likely to be the cause of your pain. Usually, someone with arthritis will fulfill at least three of these six criteria along with their knee pain:
Greater than 50 years of age
Morning stiffness for less than 30 minute
Cracking and popping of the knee
Tenderness over the bones of the knee
No warmth to the knee
If you have three of these symptoms, you then are more likely to have arthritis.
A tumor of the knee is (ie bone cancer) is much more common in children but there are some forms that can occur in adults. I cannot tell you that it is not a tumor but it is much less likely to be this than arthritis.
I do think that your doctor should order an xray of your knee. This will give you an indication as to whether arthritis is present (or, in the unlikely case, a tumor). Given the amount of pain medication you are requiring, further workup should be done in my opinion. If your doctor does not seem to be wanting to do the workup, see an orthopedic specialist if you can.
If you have arthritis, there are other treatments--bracing, injections and physical therapy
Please feel free to ask any follow up questions,
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