Painful cyst in left knee adjacent to posterior horn of medial meniscus. no meniscus tear (confirmed via mri & arthroscopy). treatment options?

Two options: 1-injection of steroid in the cyst with attempt to empty it the same time. 2-excision of the cyst. I would prefer the excision because they send to pathology and see what is it.

See below:: Most cysts in the back of the knee are due to knee joint causes, which improve as the causes is treated. So my recommendations would be: 1: do nothing except maybe pain meds, for 3 months; if no improvement, then; 2: aspiration (removing fluid) under ultrasonic guidance for fluid/needle biopsy; or; 3: removal of the cyst through the back of the knee, to get tissue for biopsy.