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Baker’s cyst

Knee joint swelling rarely comes alone

Sometimes patients feel a small, sometimes larger, bump in the back of the knee without any noticeable previous disease or injury. This is a so-called Baker’s cyst. The protrusion is palpably filled with fluid, but often does not cause any discomfort. Only when the swelling presses on nerves and vessels can it lead to pain and complications. Baker’s cyst is not a disease in itself, but a symptom that indicates the presence of other diseases or tissue weaknesses. The increased production of synovial fluid in the knee creates a bulge in the joint capsule, which fills with the natural synovial fluid.

A Baker’s cyst that has developed is treated symptomatically and, up to a limited size, can be alleviated with rest, pain medication, and physical therapy (physiotherapy), provided that good preventive care is subsequently taken. Permanent healing of Baker’s cyst, on the other hand, requires surgical removal.

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Table of Contents:

What is a Baker’s cyst?
Causes: How does a Baker’s cyst develop?
Symptoms of a Baker cyst

Diagnostics and therapy for Baker’s cyst
Treatment of a Baker cyst at the Orthopedic Center Munich East (OZMO)

What is a Baker’s cyst?

In medicine, cysts are the body’s own outgrowths as cavities that are usually filled with fluids or tissue but would not normally be present. They can occur in many organs and body tissues and are considered benign. As they grow, however, they can cause problems by pressing on surrounding tissues, nerves and blood vessels.

Baker’s cyst was first described by the English surgeon William Baker in the 19th century and named after him accordingly. It appears as a protrusion in the back of the knee and traps synovial fluid from the knee joint. For smooth movement, the knee joint must form a closed system in which the synovial fluid is present as a “lubricant” and source of nutrients between the cartilage-covered joint parts, the condyle and the socket. To keep this fluid there, each joint is enclosed by a joint capsule, which consists of a specific connective tissue.

If this tissue is weakened, it cannot sufficiently resist the internal pressure. The weak spot in the joint tissue is stressed by the pressure created in the joint capsule when too much synovial fluid (synovium) is produced, and expands to form a protrusion that can be felt in the back of the knee as a Baker’s cyst. Typically, the Baker’s cyst emerges from between the large posterior thigh muscle and the calf muscle.

Causes: How does a Baker’s cyst develop?

Basically, the joint capsule is a comparatively stable tissue. However, if the knee joint is overstimulated by inflammation or damaged by injury, the tissues strive to improve protection and secrete more joint fluid than normal. However, because space in the joint capsule is limited, there is increased pressure that the connective tissue-like envelope must withstand. If the fabric is weakened, it will not crack, just like an old rubber, but the fabric will thin. This area yields slightly to the outside and fills with excess synovial fluid, creating the typical bulge of the Baker’s cyst.

The causes of knee joint swelling such as Baker’s cyst can be varied. On the one hand, accidents and injuries can cause bleeding into the joint, resulting in the formation of a knee joint effusion with corresponding swelling. However, knee joint effusion is much more common with advanced wear of the knee joint, due to overuse and irritation of the joint. The joint also tries to “lubricate” the bumps in the cartilage caused by age-related wear with increased joint fluid. Also, unstable cartilage or meniscus parts, like a grain of sand in the eye, can irritate the joint accordingly, which also leads to increased production of synovial fluid.

Symptoms of a Baker cyst

The effusion in the knee manifests itself in a swelling usually above the kneecap, which often means that the knee can no longer be fully bent. Furthermore, there is corresponding pressure in the back of the knee. If the knee joint effusion persists chronically, it results in a bulge in the back of the knee, a so-called overflow valve called a Baker’s cyst. With this diagnosis, therefore, research must be done into the cause of why the joint is producing too much fluid. The Baker’s cyst in itself does not require surgery, since it is basically only a symptom itself.

The size of the Baker’s cyst plays a significant role in the associated consequences and symptoms. In most cases, Baker’s cyst does not cause its own symptoms, but is itself a symptom of joint diseases and injuries. The cyst size, in turn, depends on the load. A strong stress leads to an increased inflammatory reaction and at the same time to an increased formation of synovial fluid, which enlarges the Baker’s cyst. If, on the other hand, the knee is rested for some time, the size of the cyst may also decrease.

To manage the symptoms, the underlying disease should be treated as the cause. This can reduce circulatory disturbances, numbness and sensory disturbances caused by the pressure of the cyst on surrounding tissue. A Baker’s cyst, on the other hand, can only be completely removed by surgical intervention.

Diagnostics and therapy for Baker’s cyst

Diagnosis of a cyst in the popliteal fossa initially involves a patient-doctor discussion and a physical examination. Since other reasons for a swelling of this type may also be present, the Baker’s cyst must be distinguished from tumors or thromboses without any doubt. For example, an orthopedist will also use an ultrasound to examine the popliteal fossa, knee joint, and calf to accurately identify the capsular protrusion. If necessary, further procedures such as a magnetic resonance imaging (MRI) or an X-ray examination are performed. As a rule, the specialist not only examines the Baker’s cyst, but also gets an idea of possible causative diseases.

The therapy of Baker’s cyst is primarily oriented to the present symptoms. Thus, a small Baker’s cyst can often be treated by sparing the knee joint and treating the original condition. Examples of pre-existing conditions that can trigger a Baker’s cyst include osteoarthritis, meniscal damage, or arthritis. Accordingly, the physician will then also arrange for anti-inflammatory therapy with drugs or injections. If necessary, compression therapy for the knee may also be advised. However, this depends on the patient’s individual health situation, as compression can also cause problems, for example, in the case of pre-existing conditions with phlebitis or in people with an increased risk of thrombosis.

Treatment of a Baker cyst at the Orthopedic Center Munich East (OZMO)

Have you discovered a bulge in the back of the knee? Then you are welcome to make an appointment with our specialists at the Orthopedic Center Munich East (OZMO) to receive an accurate diagnosis for your diseased knee joint. Our well-equipped practice enables us to provide you with an optimal examination in one place and to initiate the appropriate measures directly afterwards. Our competent practice team will be happy to welcome you and book a suitable appointment for you for the examination and treatment of a possible Baker’s cyst.

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