Doctors think there are several reasons for this. First, the cysts have thick walls with twisted, deep roots. The body can't dissolve or absorb this tissue. There's also a valve
between the cyst and the joint. This opening allows fluid to move from the joint into the cyst.
Often other damage in the knee adds to the problem. A new study by two doctors in South Korea report better results for cyst removal using arthroscopy. A special tool with a tiny TV camera is inserted into the cyst. The fluid is taken out. Then the cyst wall is removed with a motorized shaver. Any other damage in the joint is repaired at the same time. They've had 100 percent success in treating cysts this way.