A popliteal cyst, commonly referred to as a Baker’s cyst, is a fluid-filled swelling that develops behind the knee, in the area known as the popliteal fossa. This condition is typically linked with knee joint problems, such as arthritis or cartilage tears, and results from the accumulation of excess synovial fluid the lubricating fluid in the joint. The cyst is named after the British surgeon Dr. William Morrant Baker, who first described it in the 19th century. Although a Baker’s cyst is usually not dangerous, it can cause discomfort and restrict movement, especially in more severe or chronic cases (1).
Symptoms
Baker’s cysts can range from being asymptomatic to causing significant discomfort. Some people may only notice a swelling behind the knee, while others experience pain or restricted movement (1). Common symptoms include
- Swelling or a lump behind the knee that may increase in size with activity or prolonged standing
- A feeling of tightness or stiffness
- Pain in the knee, especially when fully extending or flexing the leg
- Occasionally, the cyst can rupture, releasing fluid into the calf muscles, causing
- Sudden sharp pain
- Redness or bruising in the calf
- Swelling and a feeling similar to deep vein thrombosis (DVT)
Because symptoms of a ruptured cyst can mimic DVT, a potentially serious condition, medical evaluation is essential.
Causes
Baker’s cysts are not a primary disease but rather a manifestation of an underlying knee problem. The most common cause is an overproduction of synovial fluid due to inflammation or injury (2). This fluid gets trapped and forms a cyst. Conditions that commonly lead to the formation of a Baker’s cyst include:
- Osteoarthritis: the most common cause, especially in older adults
- Rheumatoid arthritis
- Meniscal tears (especially of the medial meniscus)
- Cartilage damage
- Gout or pseudogout
- Knee trauma or injury
These conditions cause the joint to produce extra synovial fluid, which can collect in a bursa (a fluid-filled sac) behind the knee, leading to the formation of the cyst.
Risk Factors
Certain factors can increase the likelihood of developing a Baker’s cyst (3). These include:
- Age: More common in people over 40, especially those with osteoarthritis
- Existing knee conditions: Individuals with arthritis, gout, or prior injuries
- Athletic activities: Sports or exercises that involve repetitive knee stress or twisting
- Occupational strain: Jobs requiring prolonged standing, kneeling, or squatting
- History of joint disorders: Previous joint infections or surgeries
Children can also develop Baker’s cysts, often without any underlying joint disease. In such pediatric cases, the cysts may resolve on their own.
Diagnosis
A Baker’s cyst is often diagnosed based on clinical examination and imaging. The healthcare provider may palpate a noticeable lump behind the knee and evaluate symptoms during a physical exam (3). To confirm the diagnosis and rule out other conditions, imaging tests are used:
- Ultrasound: Commonly used to detect fluid-filled masses and rule out blood clots
- MRI (Magnetic Resonance Imaging): Helpful in evaluating underlying joint damage such as a torn meniscus
- X-ray: While not able to show the cyst directly, X-rays can help detect arthritis or bone abnormalities
- Aspiration and analysis of fluid: In some cases, fluid may be withdrawn from the cyst to check for infection or crystal-related arthritis (e.g., gout)
It’s crucial to distinguish a Baker’s cyst from other serious conditions like DVT, tumors, or aneurysms, especially in the presence of sudden pain and swelling in the leg.
Treatment Options
The treatment of a Baker’s cyst often focuses on managing the underlying condition that caused the excess fluid in the first place (3). Treatment options include
Conservative Management
- Rest and avoidance of activities that worsen symptoms
- Ice application to reduce swelling
- Compression bandages or sleeves
- Elevation of the leg
- Nonsteroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation relief
- Physical therapy to strengthen surrounding muscles and improve knee function
Medical Interventions
- Aspiration: Drawing out fluid from the cyst using a needle under ultrasound guidance to relieve pressure
- Corticosteroid injections: Administered directly into the knee joint to reduce inflammation and fluid production
Surgical Options
Surgery is considered when conservative treatments fail or when the cyst is particularly large or painful. Surgical procedures may include (3):
- Arthroscopy: Minimally invasive surgery to address intra-articular problems such as a torn meniscus
- Cyst excision: Rarely performed, but involves removal of the cyst if it causes significant symptoms and recurs frequently
In children, surgery is rarely needed as pediatric cysts often resolve without intervention.
Living With or Prevention
Living with a Baker’s cyst can be manageable with the right strategies
Lifestyle Modifications
- Weight management to reduce pressure on the knees
- Engaging in low-impact exercises like swimming or cycling
- Wearing supportive footwear to improve joint alignment
Preventing Recurrence
- Managing arthritis or other knee problems proactively with medications and lifestyle changes
- Regular physical therapy to maintain joint mobility and muscle strength
- Avoiding high-impact activities that stress the knees
Although there’s no guaranteed way to prevent a Baker’s cyst, early treatment of knee injuries and chronic joint conditions can greatly reduce the risk. For individuals prone to cysts, staying consistent with follow-up care and monitoring is key.
References
- Verbner JM, Pereira-Duarte M, Zicaro JP, Yacuzzi C, Costa-Paz M. Infected Baker’s Cyst: A New Classification, Diagnosis and Treatment Recommendations. J Orthop Case Rep. 2018 Nov-Dec;8(6):16-23. doi: 10.13107/jocr.2250-0685.1238. PMID: 30915286; PMCID: PMC6424320.
- Lee BI, Seo JH, Kim YB, Seo GW. A potential risk factor of total knee arthroplasty: an infected Baker’s cyst – a case report. BMC Musculoskelet Disord. 2020 Feb 29;21(1):137. doi: 10.1186/s12891-020-3147-2. PMID: 32113464; PMCID: PMC7049224.
- Hasan M, Berkovich Y, Sarhan B, Steinfeld Y, Ginesin E, Hijaze S, Sleiman A, Yonai Y. Comprehensive analysis of knee cysts: diagnosis and treatment. Knee Surg Relat Res. 2025 May 14;37(1):23. doi: 10.1186/s43019-025-00269-2. PMID: 40369692; PMCID: PMC12080045.
