bakers cyst what you need to know

A Bakers cyst, or popliteal cyst, is a bulging lump behind your knee. Inside the lump is a sac filled with fluid. The cyst is caused by fluid buildup in your knee joint. This can happen if you have a knee injury, such as a cartilage tear. Osteoarthritis or rheumatoid arthritis can also cause an abnormal buildup of joint fluid.

A lump or swelling in the back of your knee when you stand or walk
Knee swelling that goes away when you bend your knee
Knee pain
Stiffness or tightness in your knee that may get worse with movement

Transillumination is a test that can show if the cyst is filled with fluid. Your healthcare provider will shine a light through your cyst.
X-ray, MRI, or ultrasound pictures may be taken of the bones and tissues in your knee joint. The pictures will show any problems, such as arthritis, a knee injury, or fluid buildup. You may be given contrast liquid to help the pictures show up better. Tell the healthcare provider if you have ever had an allergic reaction to contrast liquid. Do not enter the MRI room with anything metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.