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Maryland Orthopedic Specialists
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Knee

Baker's Cyst (Popliteal Cyst)

A Baker's cyst (also called a popliteal cyst) is a fluid-filled swelling at the back of the knee caused by excess joint fluid that has accumulated in the popliteal bursa. While the name sounds alarming, Baker's cysts themselves are rarely the primary problem; they are almost always a sign of intra-articular pathology inside the knee. Treating the underlying cause is the cornerstone of management at Maryland Orthopedic Specialists.

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What is baker's cyst (popliteal cyst)?

The gastrocnemio-semimembranosus bursa sits in the posteromedial fossa of the knee. In most adults, this bursa communicates with the knee joint through a one-way valve-like opening in the posteromedial capsule. Swelling is related to irritation in the knee and overproduction of synovial fluid.

The gastrocnemio-semimembranosus bursa sits in the posteromedial fossa of the knee. In most adults, this bursa communicates with the knee joint through a one-way valve-like opening in the posteromedial capsule. When the knee produces excess synovial fluid (due to osteoarthritis, a meniscus tear, rheumatoid arthritis, or other intra-articular pathology), that fluid migrates posteriorly and distends the bursa, creating the characteristic popliteal mass.

Most common underlying causes:

  • Knee osteoarthritis (most common in adults > 40)
  • Medial meniscus tears
  • Inflammatory arthritis (rheumatoid, psoriatic)
  • Ligamentous or chondral injury producing reactive effusion

Baker's cysts may also occur in children (though often without identifiable intra-articular pathology), where they tend to be self-limiting.

Symptoms — do you recognize these?

  • Posterior knee fullness, tightness, or swelling, especially with prolonged activity
  • Pressure or aching sensation behind the knee
  • Reduced knee flexion in large cysts
  • Cyst rupture — sudden posterior calf pain, swelling, and bruising (Foucher's sign); mimics deep vein thrombosis and must be distinguished from DVT clinically and with imaging
  • In children, often an incidental, asymptomatic soft mass

Call us at (301) 515-0900. Same-day appointments available at our Bethesda and Germantown locations.

How we diagnose it

  • Clinical examination — transillumination and palpation of a fluctuant posteromedial mass; Foucher's sign (cyst disappears with knee extension, reappears in flexion)
  • Ultrasound: confirms cystic structure, rules out solid mass or vascular lesion (popliteal artery aneurysm); preferred first-line imaging; can guide aspiration
  • MRI: characterizes cyst size, communication, and identifies the intra-articular pathology driving cyst formation; necessary if intra-articular surgery is planned

Treatment options

The most effective treatment for a Baker's cyst is addressing the underlying cause: whether a meniscus tear, knee osteoarthritis, or another source of excess joint fluid. When the intra-articular pathology is treated, the cyst typically resolves on its own over weeks to months without any direct intervention. For persistent or symptomatic cysts, options include corticosteroid injection, ultrasound-guided aspiration, and in refractory cases, surgical excision.

Surgical Procedure

Knee Arthroscopy

Minimally invasive joint scope using small portals to directly visualize and treat intra-articular knee pathology (meniscal tears, cartilage defects, loose bodies, synovitis, and ligament assessment) as an outpatient procedure.

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Recovery & rehabilitation

  • Intra-articular steroid injection: A cortisone injection in the knee will often reduce swelling and pain associated with a Baker's cyst.
  • Aspiration: Immediate relief; full activity within days; recurrence common without treating underlying joint disease
  • Intra-articular surgery for underlying pathology: Cyst regression typically occurs over 4–12 weeks following joint restoration

Frequently Asked Questions

Is a Baker's cyst dangerous?
Baker's cysts themselves are not dangerous, but a ruptured cyst can produce calf pain and swelling resembling a DVT. This must be evaluated promptly. Additionally, cysts can occasionally compress the popliteal artery or common peroneal nerve in extreme cases.
Will my Baker's cyst go away on its own?
Cysts in children often resolve spontaneously. In adults, the cyst will persist or recur as long as the intra-articular pathology (meniscus tear, OA) driving excess fluid production remains untreated.
What is actually inside a Baker's cyst?
A Baker's cyst is a fluid-filled sac located at the back of the knee in the popliteal fossa. The fluid is synovial fluid (the same lubricating fluid that cushions your knee joint) that has leaked or been pushed into this space through a one-way valve between the joint and the bursa. Because the fluid originates from inside the knee, treating the underlying cause (such as a meniscus tear or arthritis) is the most effective way to resolve the cyst.
Do I need surgery to treat my Baker's cyst?
Surgery is rarely the first step for a Baker's cyst. Your MOS surgeon will focus on diagnosing and treating the underlying knee condition (such as a meniscus tear or osteoarthritis), which often causes the cyst to shrink or disappear on its own. If the cyst remains large and painful after the underlying problem has been addressed, aspiration (draining the fluid with a needle) or surgical excision may be considered. Direct removal without treating the root cause has a high recurrence rate.
Can a Baker's cyst rupture, and what happens if it does?
Yes, a Baker's cyst can rupture, causing fluid to leak into the calf. This typically produces sudden calf pain, swelling, and bruising. These symptoms can closely mimic a deep vein thrombosis (DVT or blood clot). It is important to seek prompt evaluation so that a DVT can be ruled out with an ultrasound. A ruptured cyst usually resolves on its own with rest, ice, and elevation over one to three weeks, though the underlying knee problem still needs to be addressed to prevent recurrence.

Meet the specialists

Christopher S. Raffo, MD

Christopher S. Raffo, MD

Orthopedic Surgery · Sports Medicine · Knee & Shoulder Arthroscopy · Joint Replacement

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John J. Christoforetti, MD

John J. Christoforetti, MD

Orthopedic Surgery · Sports Medicine · Hip, Knee & Shoulder Arthroscopy · Shoulder Replacement

Meet Dr. Christoforetti →
James S. Gardiner, MD

James S. Gardiner, MD

Orthopedic Surgery · Sports Medicine · Knee & Shoulder Arthroscopy · Knee Replacement

Meet Dr. Gardiner →

Related conditions

Knee OsteoarthritisMeniscus Tear
Medically reviewed by Christopher S. Raffo, MD
Last reviewed June 15, 2026

References

  1. Handy JR. "Popliteal cysts in adults: a review." Seminars in Arthritis and Rheumatism. 2001;31(2):108–118. doi:10.1053/sarh.2001.25086
  2. Sanchez JE, Conkling N, Labropoulos N. "Compression syndromes of the popliteal neurovascular bundle due to Baker cyst." Journal of Vascular Surgery. 2011;54(6):1821–1829. doi:10.1016/j.jvs.2011.06.024
  3. Herman AM, Marzo JM. "Popliteal cysts: a current review." Orthopedics. 2014;37(8):e678–684. doi:10.3928/01477447-20140728-52
  4. OrthoInfo. AAOS. "Baker's Cyst (Popliteal Cyst)." American Academy of Orthopaedic Surgeons. https://orthoinfo.aaos.org/en/diseases--conditions/bakers-cyst-popliteal-cyst
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