Synovial cysts are fluid-filled lumps that form on the top of your foot. They feel squishy to the touch, and they can get a little sore after you press on them or after your shoe puts pressure on them all day. People are often very alarmed when synovial cysts first form, but in reality, these cysts are pretty benign. That does not mean, though, that they do not need treatment. You should visit a podiatrist if you have a synovial cyst on the top of your foot.