Baker’s Cyst

By Demetria Juber, PT, DPT

Baker’s Cyst – Definition of Condition

A Baker’s Cyst, also known as a popliteal cyst, is a fluid-filled cyst that develops in the back of the knee. A cyst is an abnormal bulge, usually noncancerous growth, that is filled with liquid. The area behind the knee becomes swollen and inflamed, which can cause knee and/or calf pain, swelling around the knee, and/or clicking or locking within the knee.

Why is there Fluid in the Knee?

The knee joint is filled with clear fluid called synovial fluid. This acts like oil in a car to help the joint move without difficulty. There are also small sacs within the knee join that are filled with fluid, known as bursa. Bursa cushion the joint when standing and walking. However, these fluid-filled sacs (bursa) may be aggravated if there is a problem within the knee, such as an injury, meniscus tear, or a condition like osteoarthritis.

Baker's Cyst is lump behind the knee and can cause knee pain. JOI Rehab

Baker’s Cyst is lump behind the knee and can be painful

Baker’s Cyst Causes

A Baker’s Cyst may occur due to inflammation and swelling within the knee joint. Due to inflammation, the knee produces extra fluid (synovial fluid), which travels to the back of the knee. This fluid builds up in the bursa (popliteal bursa), which causes swelling and a bulge to form. This ultimately leads to the formation of a Baker’s Cyst.

These health conditions or injuries may cause a cyst if the excess fluid travels to the back of the knee:

  • Osteoarthritis in the knee – breakdown of the knee joint due to wear and tear of the cartilage
    • This causes the knee to produce too much fluid, which may lead to a bulge (formation of a cyst) and tightness behind the knee
  • Inflammatory Arthritis – Rheumatoid Arthritis
  • Injury – Meniscus tear or ACL tear
  • Gout – build-up of uric acid in the blood, usually affecting the big toe

Baker’s Cyst Signs And Symptoms

A Baker’s Cyst may feel like a bulge or lump in the back of the knee. Other symptoms may include:

  • Knee pain
  • Stiffness or tightness in the back of the knee that makes bending or straightening the knee difficult or painful
  • Instability – feeling the knee buckle when standing or walking like the leg wants to give out
  • Clicking or popping when bending or straightening the knee
  • Swelling in the knee or lower leg

On occasion, some people with this condition will have no symptoms and the condition is only discovered with imaging or a physical exam.

What happens if a Baker’s cyst is left untreated?

A large Baker’s Cyst will interfere with blood flow to the lower leg. This may cause swelling below the knee, in the calf, weakness, or numbness. It may even resemble symptoms of a blood clot or even pose a risk of bursting.

Diagram showing the difference in a normal knee joint compared to one with a Baker Cyst

Image of a Cyst Posterior of the Patella

How Long Does It Last?

Most Baker’s cysts go away on their own with time. However, cysts that do not go away on their own or increase in size, are usually treated with nonsurgical treatment first before surgical intervention is considered. It may take several months for the Baker’s cyst to go away on its own.

How do you treat a Baker’s cyst on your knee?

A Baker’s Cyst can be treated conservatively through activity modification and physical therapy. If the fluid does not go away on it’s own you may have to have an aspiration of the knee to drain excess fluid. Lastly, If a Baker’s Cyst continues to reappear it may require surgery for the underlying condition that is causing it.

Nonsurgical Treatment:

  • Observation to ensure the cyst does not grow larger or become more painful
  • Modifying activities and avoiding high-impact activities that irritate the knee, such as running or playing tennis.
  • Use of anti-inflammatory medications like ibuprofen to decrease pain and swelling
  • Steroid injection into knee to reduce pain and inflammation
  • Aspiration of the Baker’s Cyst – use of a needle to drain the excess fluid from the joint
  • PHYSICAL THERAPY – for strengthening your knee and improving the range of motion

Surgical Treatment:

  • Arthroscopic repair to meniscus or other conditions that are causing the formation of the condition.

What Causes A Baker’s Cyst To Burst

A Baker’s cyst can rupture if it fills up with synovial fluid too quickly. This causes increased pressure, which leads to the popliteal bursa sac to tear. After the Baker’s cyst ruptures, fluid is released into the calf. While a ruptured cyst is not common, one will experience a very intense and sharp pain in the calf muscle, similar to a blood clot or DVT. It is important to contact one’s doctor for treatment of a ruptured cyst.

Written by: Demetria Juber, PT, DPT

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