I wrote recently that I have been diagnosed with a tear in the lateral meniscus of my left knee. This is causing joint fluid to leak, so I have a cyst on the knee. The resulting persistent bump is what caused me to have it looked into. Yesterday I had a follow-up with my Orthopedic surgeon and he confirmed it is a horizontal tear in the meniscus. He said it is in an area with poor blood supply so there is no good surgical option to fix it. The options are to wait and see or remove the meniscus entirely. For now, we are going with the former. The good news is he says the arthritis in my knee has not advanced too much and I should get more good years out of the knee as long as I avoid impact loading, especially running, and keep the surrounding muscles in shape. So my exercise regimen of cycling, strength training, and hiking (careful on the downhills) is serving me well.
I did find a counter-opinion on the web that horizontal tears can be successfully repaired, so I will keep researching this issue and may seek a second opinion. There is no hurry, though, because I am asymptomatic, and the situation is not changing rapidly.