Baker Cyst

What is Baker Cyst

Baker cyst, also called a popliteal cyst, is a sac-like growth that forms at the back of the knee.

The cyst forms when the fluid-filled sac (bursa) that cushions the knee joint becomes enlarged. The bursa that becomes a Baker cyst is located at the back of the knee joint.

What are the causes?

In most cases, a Baker cyst results from another knee problem that causes swelling inside the knee. This makes the fluid inside the knee joint (synovial fluid) flow into the bursa behind the knee, causing the bursa to enlarge.

What increases the risk?

You may be more likely to develop a Baker cyst if you already have a knee problem, such as:

  • A tear in cartilage that cushions the knee joint (meniscal tear).
  • A tear in the tissues that connect the bones of the knee joint (ligament tear).
  • Knee swelling from osteoarthritis, rheumatoid arthritis, or gout.

What are the signs or symptoms?

A Baker cyst does not always cause symptoms. A lump behind the knee may be the only sign of the condition. The lump may be painful, especially when the knee is straightened. If the lump is painful, the pain may come and go. The knee may also be stiff.

Symptoms may quickly get more severe if the cyst breaks open (ruptures). If your cyst ruptures, signs and symptoms may affect the knee and the back of the lower leg (calf) and may include:

  • Sudden or worsening pain.
  • Swelling.
  • Bruising.

How is this diagnosed?

This condition may be diagnosed based on your symptoms and medical history. Your health care provider will also do a physical exam. This may include:

  • Feeling the cyst to check whether it is tender.
  • Checking your knee for signs of another knee condition that causes swelling.

You may have imaging tests, such as:

  • X-rays.
  • MRI.
  • Ultrasound.

How is this treated?

A Baker cyst that is not painful may go away without treatment. If the cyst gets large or painful, it will likely get better if the underlying knee problem is treated.

Treatment for a Baker cyst may include:

  • Resting.
  • Keeping weight off of the knee. This means not leaning on the knee to support your body weight.
  • NSAIDs to reduce pain and swelling.
  • A procedure to drain the fluid from the cyst with a needle (aspiration). You may also get an injection of a medicine that reduces swelling (steroid).
  • Surgery. This may be needed if other treatments do not work. This usually involves correcting knee damage and removing the cyst.

Follow these instructions at home:

  • Take over-the-counter and prescription medicines only as told by your health care provider.
  • Rest and return to your normal activities as told by your health care provider. Avoid activities that make pain or swelling worse. Ask your health care provider what activities are safe for you.

Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if:

  • You have knee pain, stiffness, or swelling that does not get better.

Get help right away if:

  • You have sudden or worsening pain and swelling in your calf area.
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