I had undergone an arthroscopy for a meniscule tear in my left knee in february 2019. this was the 2nd one on the same knee with the 1st having been in 2014. is it possible to still be suffering from "weakened muscles" two years later?

Disuse atrophy: Not unique to experience muscle bulk loss over anterior thigh muscles prior to or after knee surgery, but typically, there is not severe loss of strength. If this is indeed your experience, would do well to be evaluated for nerve or muscle dysfunction. Discuss initially with your orthopedic surgeon, and decide next steps.

Unusual diagnosis: There are conditions of the knee like a cruciate tear that can be helped with muscle strengthening but I do not know of a diagnosis of weakened muscles. If you never recovered from the last surgery with muscle atrophy persisting you may needed strengthening. Late onset of a weak muscle is unusual and suggests further pathology.