What Causes a Baker’s Cyst Behind the Knee?

What is a Baker’s Cyst?

A Baker’s cyst develops when excess joint fluid builds up in the popliteal bursa, a small sac located behind the knee. This fluid forms a lump that may feel tight or tender, especially when bending or straightening the knee.

These cysts are often linked to underlying knee problems, such as arthritis or cartilage tears. While they can occur in both adults and children, they’re more common in people with existing knee conditions.

6 Common Causes of a Baker’s Cyst Behind the Knee

Here are the most frequent causes of a Baker’s cyst behind the knee:

1. Knee Joint Inflammation
   When the knee joint becomes inflamed due to injury or disease, it produces extra synovial fluid. This excess fluid can collect behind the knee, forming a cyst. Conditions like rheumatoid arthritis and osteoarthritis often trigger this response.
2. Meniscus Tears
   The meniscus is a cartilage that cushions the knee joint. If it tears from sudden injury or wear and tear, it can cause irritation and fluid buildup, leading to a Baker’s cyst.
3. Knee Injuries
   Trauma to the knee, such as ligament sprains or fractures, can increase fluid production in the joint. Over time, this may result in a cyst forming behind the knee.
4. Gout or Pseudogout
   These types of inflammatory arthritis cause crystal deposits in the joint, leading to swelling. The excess fluid can contribute to the development of a Baker’s cyst.
5. Overuse or Repetitive Strain
   Athletes or people with jobs that involve frequent kneeling, squatting, or heavy lifting may experience knee stress. Over time, this can lead to joint irritation and cyst formation.
6. Infections (Less Common)
   In rare cases, infections in the knee joint can cause fluid accumulation, resulting in a Baker’s cyst. This requires immediate medical attention.

Symptoms of a Baker’s Cyst

Not everyone with a Baker’s cyst will be able to notice symptoms, but when they do, they may experience:

• A visible bulge behind the knee
• Stiffness or tightness in the knee
• Mild to moderate pain, especially when moving
• Swelling that worsens with activity
• In rare cases, the cyst may rupture, causing sharp pain and calf swelling

How Is a Baker’s Cyst Diagnosed?

Doctors typically diagnose a Baker’s cyst through:

• Physical Examination: Checking for swelling and tenderness behind the knee
• Imaging Tests: Ultrasound or MRI scans can confirm the cyst and identify any underlying knee issues
• Joint Fluid Analysis: If infection is suspected, fluid may be drawn for testing

When Should You Consult a Doctor for a Baker’s Cyst?

Most Baker’s cysts aren’t serious, but you should consult a healthcare provider if:

• The swelling gets worse or doesn’t improve
• You have severe pain, redness, or warmth around the knee
• The cyst ruptures, causing sudden calf swelling (which can mimic a blood clot)

Key Takeaway

A Baker’s cyst behind the knee usually develops due to joint inflammation, injuries, or conditions like arthritis. While many cysts resolve on their own, treating the root cause is key to preventing recurrence.

If you’re experiencing persistent knee pain or swelling, consulting an orthopedic surgeon like Barrett S. Brown, M.D. can help determine the best treatment plan. With expertise in knee arthroscopy, our surgeon provides advanced care for Baker’s cysts and related knee conditions.

Would you like to learn about treatment options? Contact our office at (346) 247-2531 to schedule a consultation.