Welcome @pamgalli, a Baker's cyst is a fluid-filled growth behind the knee - https://www.mayoclinic.org/diseases-conditions/bakers-cyst/symptoms-causes/syc-20369950.

Do you have fibromyalgia? Are you trying to find some specific information?

@pamgalli Baker cysts are a buildup of fluid behind the knees. They can be drained however that is not always necessary. I did not have to have mine drained. They drained/went away on their own. I was given several core exercises and told under no circumstances was I to ride bike but can ride a stationary one. This was approximately 6 years ago at age 60. I do a lot of walking on level ground.