Baker’s Cyst - Causes, Symptoms, Treatment, and Rehabilitation

What Is a Baker’s Cyst? - Definition and Mechanism of Formation

A Baker’s cyst, also known as a popliteal cyst, is a pathological, fluid-filled cavity located at the back of the knee joint, most often between the semimembranosus muscle and the medial head of the gastrocnemius muscle. Clinically, it presents as a soft-tissue mass in the popliteal fossa that may vary in size depending on the position of the leg and the patient’s activity level. Although it can be discovered incidentally, in many cases it becomes a source of pain and functional limitations.

Unlike primary cysts, which develop independently, a Baker’s cyst is usually a secondary lesion, forming in response to an existing intra-articular pathology. Degenerative changes (e.g., gonarthrosis), chronic inflammatory conditions (such as rheumatoid arthritis), and intra-articular injuries (e.g., meniscal or cartilage damage) lead to increased production of synovial fluid. The excess fluid raises intra-articular pressure and promotes the displacement of synovial fluid through the posteromedial recess of the joint capsule, which under normal conditions serves as a flexible compensatory space.

Over time, the synovial membrane may bulge beyond the joint cavity, forming a synovial herniation that fills with fluid, creating the cyst. This structure usually appears as an elliptical, single- or multi-chambered fluid sac that may enlarge during physical exertion or prolonged knee loading.

It is important to emphasize that a Baker’s cyst is not an isolated disease, but rather a manifestation of other pathological processes occurring within the knee. Therefore, effective treatment requires not only the removal of the cyst but, above all, proper diagnosis and management of the underlying disorder.

Baker’s Cyst and Other Lesions in the Popliteal Fossa

Differentiating a Baker’s cyst from other lesions in the popliteal fossa is crucial for accurate diagnosis. Possible differential diagnoses include:

• Deep vein thrombosis of the lower limb (especially in cases of cyst rupture and fluid leakage into the surrounding tissues)
• Meniscal cysts (particularly cysts of the medial meniscus)
• Lipomas
• Ganglia
• Popliteal artery aneurysms
• Soft tissue tumors (rare, but should be ruled out in cases of irregular structures)

Because of the risk of misdiagnosis, especially when clinical presentation is atypical, appropriate imaging studies are essential – primarily ultrasound (US) and magnetic resonance imaging (MRI).

Causes of Baker’s Cyst - Conditions That Promote Its Formation

Baker’s Cyst, although not a primary condition, is a clear signal that a pathological process is taking place within the knee joint. In almost all cases, its formation is associated with an underlying disease – most often inflammatory, degenerative, or traumatic in nature. Understanding the mechanism of popliteal cyst formation therefore requires analyzing those conditions that directly or indirectly lead to overproduction of synovial fluid and increased intra-articular pressure.

One of the most common conditions associated with the formation of a Baker’s cyst is knee osteoarthritis (gonarthrosis). The degenerative process of the articular cartilage leads to chronic irritation of the synovial membrane, which in turn results in overproduction of synovial fluid. The accumulating fluid, combined with weakening of the capsular and ligamentous structures, promotes the movement of fluid into the posterior recess of the joint and the formation of a synovial membrane herniation. In this case, the cyst is a symptom of advanced degenerative joint disease and often coexists with osteophytes, limb axis deformity, and restricted range of motion.

Another frequent cause is rheumatoid arthritis (RA) and other chronic inflammatory joint diseases, such as psoriatic arthritis or systemic lupus erythematosus. In the course of these diseases, persistent inflammatory activation of the synovial membrane occurs, generating large amounts of effusion and chronic swelling of the knee joint. In such cases, a Baker’s cyst may reach considerable size and cause compression symptoms. Patients in this group are also at greater risk of cyst recurrence after conservative treatment.

Knee injuries represent another significant etiological category. Damage to the menisci – particularly the medial meniscus – and articular cartilage injuries disrupt the integrity of joint structures and trigger reactive synovitis. The result is increased synovial fluid production and possible leakage of the fluid through the posterior portion of the joint capsule. In this group, cysts secondary to sports or overload injuries are common, especially among younger and physically active individuals.

The development of a Baker’s cyst is also influenced by knee joint overload, which may result from various biomechanical and functional factors. Athletes performing intensive, repetitive flexion and extension movements of the knee (for example, runners, jumpers, soccer players) are particularly prone to micro-overloading of joint structures. Similarly, individuals with excessive body weight experience increased axial loading, which accelerates cartilage wear and leads to chronic synovial irritation. Patients with postural defects, lower limb axis deviations (valgus or varus knees), abnormal patellar tracking, or limited ankle mobility also show an increased incidence of popliteal cysts due to the uneven distribution of forces acting on the knee.

The key factor in the pathogenesis of Baker’s cyst is synovial fluid – both its volume and intra-articular pressure. Excessive fluid production, caused by inflammation, injury, or overuse, leads to the development of a so-called valvular flow mechanism – fluid moves from the joint cavity into the posteromedial recess but does not return, as the opening closes in a one-way fashion. Consequently, the fluid accumulates in an extra-articular space, forming a cyst. This mechanism also explains the frequent recurrence of cysts after aspiration alone – without treatment of the underlying disease, fluid production continues, and the cyst reappears.

Symptoms of Baker’s Cyst – How to Recognize the Problem?

Although a Baker’s cyst may remain asymptomatic for a long time, in many cases it leads to pronounced pain and functional limitations that affect the patient’s quality of life. Symptoms largely depend on the cyst’s size, the degree of fluid accumulation, and the rate of its enlargement. Mechanical factors such as knee joint tension, physical activity, and coexisting pathological changes are also significant.

One of the first symptoms patients notice is a feeling of pressure and tightness in the popliteal fossa. It may be described as a sense of “fullness” behind the knee, clearly noticeable when standing, kneeling, or after intense physical activity. As the cyst’s volume increases, discomfort intensifies, and the area behind the knee may become visibly swollen and tender to touch.

Another characteristic symptom is pain beneath the knee during flexion, particularly during activities requiring deep squatting, climbing stairs, or sitting with knees bent at a right angle. Pain may also worsen after prolonged standing or walking, when intra-articular pressure and cyst volume increase. In the supine position or after rest, pain often subsides, which can be misleading and delay diagnosis.

A reduced range of knee motion is another symptom suggesting the presence of a cyst. This may involve flexion (the cyst may mechanically limit movement by pressing against the posterior joint wall) or extension – patients often describe a feeling of “pulling” or blocking when attempting full leg extension. Some may develop an altered gait pattern – the knee held in slight flexion – which can lead to secondary strain in the hip joint and spine.

Complications of Baker’s Cyst

Complications of Baker’s cyst, although rare, can have serious clinical consequences and require urgent differential diagnosis. The most common and alarming complication is cyst rupture, leading to leakage of synovial fluid into the posterior compartment of the calf. Symptoms may resemble deep vein thrombosis: sudden severe calf pain, swelling, tenderness, and a feeling of tightness in the skin. In such cases, an urgent Doppler ultrasound is necessary to exclude thrombosis and confirm the presence of perimuscular fluid. A ruptured cyst is not life-threatening but requires proper anti-inflammatory treatment and limitation of limb loading.

Another possible complication is compression of the tibial nerve, which runs close to the popliteal fossa. This may cause neurological symptoms such as paresthesia, numbness, or sensory weakness in the calf and foot. In advanced cases, there may be dysfunction of the foot flexor muscles.

An important element of clinical assessment is the evaluation of cyst size. Small cysts (up to 1–2 cm) often cause no symptoms and are detected incidentally during imaging for other reasons. Larger cysts (over 3–4 cm) usually cause compressive symptoms, limited motion, and pain. The rate of cyst enlargement is also significant – a rapidly expanding cyst can cause more severe discomfort than a cyst of the same size that grows gradually, allowing surrounding tissues to adapt.

Diagnosis of Baker’s Cyst – What Tests Are Needed?

Effective diagnosis of Baker’s cyst is based on a combination of clinical history, physical examination, and appropriately selected imaging studies. Since a popliteal cyst is in most cases a manifestation of another knee pathology, it is essential not only to confirm its presence but also to identify its cause. The assessment includes the cyst itself, intra-articular structures, the vascular system, and surrounding soft tissues.

Physical examination remains the basis of preliminary diagnosis, allowing for quick identification of typical clinical features. During palpation, the physician detects a soft, elastic, usually non-painful mass in the popliteal fossa – between the medial head of the gastrocnemius muscle and the semimembranosus muscle. The swelling may increase in volume when the knee is extended and decrease during flexion, which also facilitates diagnosis. The range of knee motion is assessed – in larger cysts, limited full extension or a “blocking” sensation at the end of movement is often observed. Pain with deep flexion or prolonged standing may indicate compressive pathology.

Ultrasound (USG) is currently the method of choice for diagnosing Baker's cysts. It is a quick, non-invasive test that is well tolerated by patients and widely available in outpatient practice. USG not only confirms the presence of a cyst, but also assesses its size, contents (homogeneous fluid, with septa or clots), number of chambers, tension, and possible connection to the joint cavity. Importantly, ultrasound also allows differentiation of cysts from other soft tissue lesions, as well as targeted puncture under controlled aspiration conditions. If a cyst rupture or fluid in the posterior compartment of the calf is suspected, ultrasound allows assessment of the extent of transudate and exclusion of complications.

In more complex cases or when a detailed assessment of the knee joint is necessary, magnetic resonance imaging (MRI) is used. This is a highly sensitive and specific examination that allows for accurate assessment of the cyst – its location, size, internal structure, and relationship to surrounding tissues. MRI is indispensable in the assessment of accompanying changes: damage to the menisci, articular cartilage, ligaments, and synovial membrane. It also allows for the exclusion of neoplastic changes, the presence of deposits, or loose bodies in the joint. When planning surgical treatment, magnetic resonance imaging is the gold standard for diagnosis, especially if there are neurological symptoms or significant movement limitations.

An important element of Baker's cyst diagnosis is differential diagnosis. In clinical practice, it is sometimes necessary to distinguish this lesion from other pathologies that may present a similar clinical picture:

• Deep vein thrombosis of the lower limb – especially in the case of a ruptured cyst, the symptoms (pain, swelling, calf tension) can be very similar. In such cases, a Doppler ultrasound is necessary.
• Meniscus cysts – usually located more laterally, often associated with damage to the internal structure of the meniscus.
• Popliteal artery aneurysms – pulsating nature of the lesion, possible vascular murmurs. They require exclusion by Doppler or angio-MRI.
• Soft tissue tumors – solid lesions, often irregular, without communication with the joint cavity.

In clinical practice, the following should be indications for extended imaging diagnostics:

• presence of neurological symptoms (numbness, limb weakness),
• significant limitation of knee mobility,
• suspicion of complications (cyst rupture, infection),
• no improvement despite conservative treatment,
• the need to plan surgical or injection treatment.

In summary, accurate diagnosis of a Baker’s cyst relies on a comprehensive approach, where physical examination is the starting point, ultrasonography provides confirmation and monitoring, and MRI offers an in-depth assessment of knee structures and treatment planning. Only such a strategy allows effective differentiation and the selection of the most appropriate therapeutic approach.

Treatment of a Baker’s Cyst – Conservative and Interventional Methods

Treatment of a Baker’s cyst requires a comprehensive approach in which the main goal is not only to remove the cyst itself but, above all, to eliminate the cause of its formation. Since a popliteal cyst in most cases accompanies another pathological process within the knee – such as inflammation, degeneration, or mechanical damage – causal treatment aimed at reducing synovial fluid production and preventing recurrence is essential.

Causal treatment – controlling inflammation

The first and fundamental step in treating a Baker’s cyst is controlling the inflammatory process within the knee. In degenerative diseases such as gonarthrosis, the goal is to limit cartilage degeneration. In rheumatic diseases such as rheumatoid arthritis, effective immunomodulatory therapy is necessary to reduce inflammatory activity and joint effusion.

Regardless of the cause, the basis of conservative management is anti-inflammatory pharmacotherapy – primarily using nonsteroidal anti-inflammatory drugs (NSAIDs). These can be applied topically (as gels or ointments) or systemically (orally), with the aim of reducing pain, swelling, and synovial fluid production. NSAIDs are particularly useful during symptom flare-ups but should be used according to individual medical recommendations due to potential side effects (gastrointestinal, renal).

Aspiration of the cyst – when and how to perform the procedure

In symptomatic cysts causing pain, limited motion, or compression of surrounding structures, puncture and aspiration of the cyst can be performed. This involves inserting a needle and draining the accumulated fluid, typically under ultrasound guidance to ensure precise needle placement and evaluation of cyst contents (serous fluid, septations, or blood admixture).

Often, immediately after aspiration, a corticosteroid injection is administered, which exerts anti-inflammatory effects and inhibits synovial fluid production. It can be injected directly into the cyst or, if joint pathology is present, into the joint cavity. This often provides rapid symptom relief and reduces recurrence risk, particularly when combined with physiotherapy and treatment of the underlying condition.

However, it should be emphasized that aspiration alone does not eliminate the cause of cyst formation – without causal therapy, recurrences are relatively common.

Surgical treatment – when is surgical intervention necessary

In situations where conservative treatment and punctures do not bring about lasting improvement, surgical treatment of the popliteal cyst is considered. Depending on the nature and extent of the lesion, two main methods are possible:

Knee arthroscopy – used when the cyst coexists with intra-articular pathology, e.g., meniscus damage, diffuse synovitis, or degenerative cartilage changes. Arthroscopy not only allows the primary cause of the problem to be removed, but also closes the opening leading to the cyst, thus reducing the risk of recurrence.

Open excision of Baker's cyst – performed less frequently, mainly in cases of large, recurrent cysts that do not respond to other forms of treatment or when the cyst causes severe compression symptoms (e.g., neurological disorders, vascular symptoms). The procedure involves the surgical removal of the entire cyst, taking care to avoid the nerves and vessels in the area.

Indications for surgical treatment of Baker's cysts include:

• recurrent cysts despite repeated aspirations and steroid therapy,
• significant limitation of knee joint movement,
• severe pain and neurological symptoms (e.g., paresthesia, numbness, muscle weakness),
• suspicion of neoplastic change or unclear MRI image,
• coexisting intra-articular damage requiring arthroscopic treatment.

Rehabilitation in Baker’s Cyst – When and How to Begin Therapy?

Rehabilitation of the knee after a Baker’s cyst is an indispensable element of comprehensive treatment, both following conservative and interventional therapy. Its main goal is not only to restore full knee function but also to prevent recurrence by eliminating overload factors, improving movement biomechanics, and stabilizing the limb functionally. A well-planned and consistently implemented rehabilitation program should begin as early as possible – after pain subsides and effusion is reduced.

After aspiration or conservative treatment, physiotherapy should focus on reducing joint overload, restoring normal range of motion, and reactivating weakened muscle groups. Special attention should be given to the quadriceps, whose weakness may disrupt joint mechanics and increase posterior knee pressure.

At the early stage of therapy, isometric and proprioceptive exercises should be introduced. Proprioceptive training – using unstable platforms, sensory cushions, or functional tasks – improves neuromuscular control and limb stability during movement. In subsequent phases, dynamic and strengthening exercises are added, with loads adjusted individually.

Many patients with Baker’s cysts exhibit lower limb axis abnormalities that predispose them to medial knee overload, where the cyst most commonly forms. Rehabilitation should therefore aim not only to strengthen muscles but also to reeducate gait, correct movement patterns, and teach proper foot roll mechanics. For overweight patients, dietary consultation and a weight reduction program are recommended to decrease joint load during walking.

Modern physiotherapeutic technologies can significantly support rehabilitation by improving microcirculation, reducing tissue tension, and accelerating regeneration. Depending on the patient’s needs and treatment stage, shockwave therapy (not applied directly to the cyst but to associated tendon or enthesis overload), therapeutic ultrasound, electrotherapy (TENS, interferential currents), and TECAR radiofrequency therapy can be used.

Rehabilitation After Surgical Treatment of a Baker’s Cyst

Following surgery – either arthroscopic or open – carefully planned rehabilitation is essential to restore full range of motion, rebuild muscle strength, eliminate compensations, and prevent recurrence through improved biomechanics. Early postoperative stages include passive and active-assisted movements, patellar mobilization, unloading exercises, and proprioception training. In subsequent weeks, functional, dynamic, and gait-training exercises with full limb loading are introduced. Full return to activity, recreational or professional, depends on the course of recovery and patient discipline but usually takes several weeks to several months.

Baker’s Cyst in Different Patient Populations – Athletes, Seniors, and RA Patients

Baker's cysts can occur in patients of very different ages and functional groups, but the mechanisms of their formation, clinical course, and therapeutic goals vary significantly depending on the context. Effective treatment therefore requires an individualized approach, both in terms of diagnosis and rehabilitation. Particular attention should be paid to three key groups: athletes, the elderly, and patients with rheumatoid arthritis (RA).

Baker's cyst in athletes – overload, biomechanics, and safe return to activity

In athletes, Baker's cyst most often develops as a result of chronic overload of the knee joint. Repetitive microtrauma, excessive training intensity, insufficient recovery, or poor technique when performing exercises that put stress on the knee (e.g., squats, running, jumping) lead to activation of the synovial membrane and overproduction of joint fluid. If this fluid moves to the posterior recess of the joint and accumulates there, a typical cyst forms. In this group of patients, it is important to implement preventive and educational measures at an early stage – analysis of movement patterns, correction of technique, appropriate planning of training periodization. Conservative treatment, including pharmacotherapy and physiotherapy, usually brings good results, but a full return to sport should take place under the supervision of a sports physiotherapist and only after an assessment of functional readiness for exercise.

Eccentric exercises, proprioception training, and re-education of gait and running patterns are an indispensable part of therapy for athletes. In the case of severe symptoms or recurrence of cysts, aspiration and sometimes surgical treatment are considered, especially if simultaneous meniscus damage or articular cartilage changes are found.

Baker's cyst in seniors – a result of gonarthrosis and cautious rehabilitation

In older people, popliteal cysts most often develop as a result of advanced osteoarthritis of the knee joint (gonarthrosis). Progressive cartilage wear, inflammatory reaction of the synovial membrane, and effusion into the joint cavity promote cyst formation. In this group of patients, pain and limited knee mobility are often chronic and significantly affect quality of life, hindering daily activities.

Treatment should be aimed at slowing the progression of osteoarthritis, reducing inflammation, and strengthening the muscles of the lower limb. Due to age and frequent comorbidities, pharmacotherapy must be conducted with caution, taking into account the risk of NSAID side effects.

Rehabilitation in older people should take into account performance limitations, balance deficits, and the risk of falls. Gentle strengthening exercises, postural stabilization training, and safe gait training are implemented. Physical therapy—including electrotherapy, ultrasound, and TECAR therapy—can be a valuable adjunct to treatment, especially for pain reduction and improved comfort of movement.

Baker's cyst in patients with RA – chronic inflammation and risk of recurrence

In patients with rheumatoid arthritis (RA), Baker's cysts are usually chronic and recurrent, resulting from persistent inflammatory activity of the synovial membrane. Overproduction of joint fluid and structural changes in the joint capsule and menisci contribute to the persistence of the cyst and increase the risk of rupture. Baker's cysts in patients with RA often grow to a large size and cause compression symptoms.

Treatment in this group requires close cooperation between a rheumatologist and an orthopedist. It is crucial to maintain remission of the underlying disease, which reduces the volume of joint fluid and decreases tension within the cyst. Aspiration of fluid from the cyst and steroid injections may bring short-term improvement, but they are not a substitute for immunosuppressive therapy.

Rehabilitation should be tailored to the stage of the disease – during flare-ups, it focuses on protecting the joint and reducing swelling, and during remission, on restoring function, improving strength, and range of motion. Physical techniques (e.g., high-energy laser therapy, ultrasound) can support symptomatic treatment.

Individualization of therapy – different goals, different strategies

Despite the common diagnosis of Baker's cyst, therapeutic goals and treatment methods vary greatly depending on the patient. For an athlete, the goal is a quick and safe return to activity; for a senior citizen, it is to regain function in everyday life; and for a patient with RA, it is to control inflammation and prevent further joint damage.

That is why an interdisciplinary approach combining knowledge from the fields of orthopedics, rheumatology, physiotherapy, and sports medicine is necessary. Personalizing therapy not only increases its effectiveness, but above all reduces the risk of recurrence and unnecessary interventions.

Summary and Final Recommendations

A Baker’s cyst is not a disease entity in itself but a visible manifestation of intra-articular pathology – most often inflammatory or degenerative. Regardless of patient group, effective management requires identifying and treating the underlying cause. Removal of the cyst alone – whether by aspiration or surgery – without addressing the primary disorder usually results in recurrence. Physiotherapy occupies an essential role in both conservative treatment and postoperative rehabilitation. Strengthening knee-stabilizing muscles, improving gait biomechanics, proprioceptive training, and the use of modern physical therapy significantly improve therapeutic outcomes and reduce recurrence risk.