A cyst is a collection of fluid in a small sac. A Popliteal Cyst is a soft, often painless bump seen in the Popliteal area (back side of the knee). It is also referred to as a bakers cyst. The weakening of the joint capsule in the damaged area can cause the small sac of fluid to form. It can increase in size over a period of time.
Swelling behind the knee, discomfort or minimal pain
MRI of the knee will confirm the diagnosis but it is rarely indicated.
Usually no treatment is needed except observation.
If the cyst is painful, the goal of treatment is to correct the problem, such as arthritis or a meniscus tear. Sometimes, a cyst can be drained (aspirated) or, in rare cases, removed with surgery if it becomes very large or causes symptoms.
Rupture & increase in size.