How do you get a cyst in the knee?
In many cases, the cyst produces no symptoms, says WebMD. However, when the symptoms appear, they include slight pain, swelling and tightness behind the knee. In some situations, the sac containing the fluid tears, draining the fluid into the tissues of the lower leg. This leads to redness and swelling in the lower leg.
Sources: webmd.com, mayoclinic.org, healthline.com