What is a Baker’s cyst?

Popliteal cyst is a distend bursa or herniation of synovial membrane through the posterior part of capsule of the knee or escape of fluid through normal communication of bursa with the knee. It is filled with synovial inside the knee joint (semimembranosus or medial gastrocnemius bursa) most common in children aged 4 to 7 years and in adults aged 35 to 70 years. More common in adults than in children.

Causes of Baker’s Cyst

A Baker’s cyst is caused when excess joint fluid is pushed into one of the small sacs of tissue behind the knee. When this sac fills with fluid and bulges out, it is called a cyst.

Baker’s cyst commonly occurs with:

• A tear in the meniscal cartilage of the knee
• Knee arthritis (in older adults)
• Rheumatoid arthritis
• Other knee problems

Baker’s cyst diagnosis

During a physical exam, the health care provider will look for a soft lump in the back of the knee.

• If the cyst is small, comparing the affected knee to the normal knee can be helpful.
• There may be a decrease in range of motion caused by pain or by the size of the cyst.
• In some cases there will be catching, looking, pain or the signs and symptoms of a meniscal tear.
• Shining a light through the cyst (trans illumination) can show that the growth is fluid filled.

If the lump grows quickly, or you have night pain, severe pain, or fever, you will need more tests to make sure you do not have other types of tumors.

X-rays will not show the cyst or a meniscal tear, but they will show other problems that may be present, including arthritis. MRIs can help the health care provider see the cyst and look for any meniscal injury.

Baker’s Cyst Treatment

A Baker’s cyst may go away on its own.

If arthritis or another problem is causing the Baker’s cyst, your doctor may treat that problem. This usually makes the pain and swelling of a Baker’s cyst go away.

If a cyst does not go away, or if it is causing a lot of pain, your doctor may drain the fluid with a needle. You also may be given a shot of steroid medicine to reduce swelling. You may need to use a cane or crutch and wrap you knee in an elastic bandage. In rare cases, a baker’s cyst is removed by surgery.

There are things you can do at home to help you feel better.

• Rest your knee as much as you can.
• Take over-the-counter medicines to reduce pain and swelling. These include ibuprofen (Advil, Motrin) and naproxen (Aleve).
• Use a cane, crutch, walker, or another device if you need help to get around. These can help rest your knee.
• If you wear an elastic bandage around your knee, make sure it is snug but not so tight that your leg is numb, tingles, or swells below the bandage. Loosen the bandage if it is too tight.
• Follow your doctor, instructions about how much weight you can put on your knee
• Stay at a healthy weight. Being overweight puts extra strain on your knee.