Posterior horn medial meniscus with myxoid degeneration, what is this?

Meniscal Degeneratio: It sounds like you are describing an MRI finding on a radiologist report. It means, that on imaging, the substance of the meniscus in the inside (medial) and posterior (back) part of your knee is starting to degrade. This is a normal occurrence starting in your twenties. In the absence of a tear, this finding should be asymptomatic and should not require surgery

Medial meniscus: Sounds like a knee problem form wear and tear and age.