A Baker’s cyst, also called a Baker’s cyst or a popliteal cyst, forms under the knee and is easy to palpate. It poses no immediate health risk, but can sometimes damage blood vessels and nerves, so should be seen by a doctor.

Too much synovial fluid in the joint cavity cancause a cyst to form . A cystmay arise as a result ofan injury, inflammation, or a chronic disease affecting the osteoarticular system. The most vulnerable to this disease are athletes and people who are quiteoverweightand who are not very active in physical activity. Children from 4 to 7 years old and adults from 35 to 70 years are most often mentioned in the risk group. The cyst can be primary or secondary. Primary – developing in healthy knee joints, may be called theBaker idiopathic cyst. Fluid from inside the joint enters the popliteal bursa and forms a cyst. Secondary – develops in the arthritic knee (osteoarthritis,rheumatoid arthritis) or cartilage damage. Such a cyst may be called a secondary cyst.

What is a Baker’s cyst?

A Baker’s popliteal cyst, also referred to as a cyst, is a non-physiologically enlarged, fluid-filled, nodular, connective tissue space located at the popliteal fossa of the knee joint. It is a benign, non-cancerous, small lesion, sufficient to be detected by skin palpation. Most often it is located between the medial head of the gastrocnemius muscle and the semimembranous muscle. The knee joint is the largest joint in the human body, so pathological conditions in the form of overloads, injuries and degenerative changes are very common.

In cases of excessive production of synovial fluid, pressure inside the joint increases, limiting its flexion movements and fluid escape through the places of weakened resistance in the joint capsule. Then it accumulates in the bursae of the popliteal fossa or causes the formation of hernias in the capsule. The cyst can also rupture and leak fluid around the calf. Such pathology is present in up to 50% of adults who report symptoms.The popliteal cystusually develops at the age of 4-7 in children and in adults aged 35-70. Quickly diagnosed and properly treated, it can protect the patient from advanced lesions, the only effective treatment of which is surgery.

The causes of Baker’s cyst

The causes of thepopliteal cystaren’t fully understood. There are factors that may contribute to the increased production of synovial fluid, damage to the articular capsule and the development of Baker’s cyst. We include among them:

• intra-articular diseases (degenerative changes, rheumatoid arthritis, gout),
• abnormal valve mechanism of the joint capsule, causing one-way flow of fluid,
• damage to the back wall of the knee joint capsule (capsular hernia),
• bursitis in the popliteal fossa,
• inflammation, overload and injuries of the knee joint.

The most vulnerable to the formation of acyst under the kneeare athletes and overweight people, due to excessive stress on the knee joints. Depending on thecause of a Baker’s cyst, the structure of its wall can vary considerably. Popliteal cysts can be divided into:

• fibrous – they have a wall of 1-2 mm, made of fibrous tissue, which has a smooth, shiny inner surface,
• synovials – with a wall 2-5 mm thick, less shiny, with cosmic formations,
• inflammatory – they are surrounded by a 8 mm thick wall, which seems to be plush, “shaggy” from the projections covering it, cartilage and bone-like elements may form in it.

Baker’s cyst – symptoms, treatment

The first and basic symptomof a Baker’s cystis a lump under the knee, well palpable on palpation. The skin around this area may be red and unnaturally warm. In some cases, you may experienceswellingand discomfort when trying to bend your knee.In a later stage of the disease, limb numbnessand sensory disturbance may appear . If the contents of the cyst spill into the adjacent tissues, the calf is also numb. The basic examination to diagnose this disease is an ultrasound.Treatment of cysts depends on the degree of their advancement and ailments. It happens that the cyst disappears or the accompanying symptoms are minimal and the doctor will not recommend pharmacotherapy.

Treatment of Baker’s cyst

The diagnosis of Baker’s cystof the disease is generally not difficult after conducting a medical history and examining the patient. In doubtful cases, additional examinations are performed, in the form ofultrasound of the popliteal fossa, X-ray with contrast, thanks to which it is possible to detect a possible connection of the joint cavity with the cyst and diagnostic puncture, i.e. puncture of the cyst with a needle.

Sometimes, in order to determine thecause of the popliteal cyst formation, MRI or even arthroscopy may be ordered. Treatment depends primarily on the severity of symptoms; if symptoms are relatively mild and do not interfere with daily life, conservative treatment is sufficient. It includes limiting physical exertion and relieving the knee joint, rehabilitation and pharmacotherapy. The doctor may decide to puncture the cyst and suck out the fluid remaining in it (puncture) and inject a steroid into its area to relieve inflammation. A singlepuncture of the cystunder the kneeis unlikely to bring any immediate effect, so the procedure must be repeated several times.

Surgery for Baker’s cyst

Treatment of Baker’s cystsshould always be started with a conservative method, which may bring a good therapeutic effect in the initial stage of the disease. If treatment does not bring lasting improvement, or it is alarge cyst below the knee, surgery is the generally accepted treatment.Surgical treatment of a popliteal cystis most often carried out using the arthroscopic method. It consists in removing the cyst, closing its connection with the joint, suturing the damaged joint capsule tightly or sewing it onto the damaged site of the own graft, e.g. from a muscle.

Additionally, the hypertrophied, inflamed synovium can be removed from a separate cut of the skin. The procedure is performed under local or general anesthesia. Usually, it does not require hospitalization and the patient returns home on the same day. After the procedure, the knee will be bandaged, and the doctor can also put on a brace. Self-absorbable sutures are usually applied, others require removal after about two weeks. The method of arthroscopic treatment includes the treatment of many intra-articular diseases, allows for the least invasive removal of all causes of cyst formation, which significantly improves the effects of treatment, reduces postoperative ailments, ensures early return to the full range of mobility and activity, as well as short hospitalization.

Rehabilitation in the Baker’s cyst

Rehabilitation is indicated in the early developmental study of the disease and should include:

• in the period of acute inflammation, securing the knee joint with a soft orthosis to relieve it and reduce pain. Compression bands are also used in the area of ​​the cyst to protect it from enlargement,
• pharmacotherapy—anti-inflammatory drugs and drugs that decongest the cysts under the knee , which are administered inside and lead to fibrosis of the cyst wall and its final closure. Usually, it is enough to perform three treatments to achieve the desired therapeutic effect,
• In physical therapy, analgesic and regenerative treatments are important, in order to reduce pain, swelling and heat in the joint, cryotherapy is used, i.e. cold treatment. Iontophoresis, i.e., the administration of an anti-inflammatory drug with direct current, can be used. The following are recommended treatments that accelerate healing and regeneration: magnetic field, laser therapy, and ultrasound. If there is a need to strengthen the weakened muscles of the knee joint, electrostimulation with low-frequency currents can be used,
• kinesitherapy—in the initial stage of rehabilitation, it is best to perform gentle exercises with the therapist without weighing down: relieving on slings, isometrics, stretching, and stimulating neuromuscular stimulation. Gradually, resistance exercises are introduced to strengthen the articular capsule with the strength of the gastrocnemius and semimembranous muscles, improving the stabilization, elasticity of soft tissues, and proprioception, i.e. the feeling of the joint in space. Finally, we use exercises of the entire lower limb, increasing strength, controlling movement and working on uneven ground,
• deep tissue massage and postoperative scar,
• kneecap mobilization,
• kinesiotaping, i.e.taping, consists in wrapping the knee joint with special flexible plasters. The patches have a sensory effect that improves the local functioning of the joint. As a result of appropriate application to the knee joint, the patches will provide better stabilization, improve healing processes and reduce pain.