What are the signs someone has baker's cyst?

Swelling behind knee: Baker's cyst form over the back and inside aspect of the knee (posteromedial) just to the midline of the hamstring tendons. The common symptoms are swelling, fullness in the back of the knee, and/or pain/tightness with knee bending. Baker's cyst can grow or shrink in size often related to activtiy.

Swelling: A bakers cyst is an accumulation of fluid in the back of the knee. Typically described as a sensation of fullness behind the knee.