What Causes Pus Filled Lumps Under The Knee?

Hii have pus water filled bumps under my knee. When they get big i pop them or squeeze it. My skin flakes as it trys to heal.. it comes and goes every few months. I used to strip dance so I thought it was due to me being on my knees a lot but I haven t been dancing in 4 mths. I have gen. Herpes. I am African American when the area goes away it leaves a dark scar. Is this a bacterial infection or an outbreak on my knee?