Baker's cyst
Encyclopedia
A Baker's cyst, also known as a popliteal
cyst
, is a benign swelling of the semimembranous or more rarely some other synovial bursa found behind the knee joint
. It is named after the surgeon
who first described it, William Morrant Baker
(1838–1896). This is not a "true" cyst
, as an open communication with the synovial sac is often maintained.
or cartilage
(particularly a meniscus
) tear. Baker's cysts can rarely be associated with Lyme disease
. Baker's cysts in children do not point to underlying joint disease. Baker's cysts arise between the tendons of the medial head of the gastrocnemius
and the semimembranosus muscle
s. They are posterior to the medial femoral condyle
.
The synovial
sac of the knee joint can, under certain circumstances, produce a posterior bulge, into the popliteal space
, the space behind the knee. When this bulge becomes large enough, it becomes palpable and cystic. Most Baker's cysts maintain this direct communication with the synovial
cavity of the knee, but sometimes, the new cyst pinches off. A Baker's cyst can rupture and produce acute pain behind the knee and in the calf and swelling of the calf muscles
.
Diagnosis is by examination. A baker's cyst is easier to see from behind with the patient standing with knees fully extended. It is most easily palpated (felt) with the knee partially flexed. Diagnosis is confirmed by ultrasonography
, although if needed and there is no suspicion of a popliteal artery
aneurysm
then aspiration of synovial fluid from the cyst may be undertaken with care. An MRI
image can reveal presence of a Baker's cyst.
A burst cyst can cause calf pain, swelling and redness that may mimic thrombophlebitis
or a potentially life-threatening deep vein thrombosis
(DVT) which may need to be excluded by urgent blood tests and ultrasonography. Although an infrequent occurrence, a Baker's cyst can compress vascular structures and cause leg edema and a true DVT.
to reduce its size, then injected with a corticosteroid
to reduce inflammation. Surgical excision
is reserved for cysts that cause a great amount of discomfort to the patient. A ruptured cyst is treated with rest, leg elevation, and injection of a corticosteroid into the knee. Recently, prolotherapy
has shown encouraging results as an effective way to treat Baker's cysts and other types of musculoskeletal conditions.
Baker's cysts in children, unlike in older people, nearly always disappear with time, and rarely require excision.
, a.k.a. Tylenol
(c) (acetaminophen), or with the additional anti-inflammatory
action (such as ibuprofen
or naproxen
), may be used. Stronger non-steroidal anti-inflammatory drug
s may be required by prescription
from one's general practitioner
.
on a low setting for 10–20 minutes may relieve some pain, but only if instructions are followed carefully.
.
Popliteal fossa
The popliteal fossa is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia.-Boundaries:The boundaries of the fossa are:-Roof:...
cyst
Cyst
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...
, is a benign swelling of the semimembranous or more rarely some other synovial bursa found behind the knee joint
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
. It is named after the surgeon
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
who first described it, William Morrant Baker
William Morrant Baker
William Morrant Baker was an English physician and surgeon. He first described the condition now known as Baker's cyst.-Life:...
(1838–1896). This is not a "true" cyst
Cyst
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...
, as an open communication with the synovial sac is often maintained.
Cause
In adults, Baker's cysts usually arise from almost any form of knee arthritisArthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....
or cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
(particularly a meniscus
Meniscus (anatomy)
In anatomy, a meniscus is a crescent-shaped fibrocartilaginous structure that, in contrast to articular disks, only partly divides a joint cavity. In humans it is present in the knee, acromioclavicular, sternoclavicular, and temporomandibular joints; in other organisms they may be present in other...
) tear. Baker's cysts can rarely be associated with Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
. Baker's cysts in children do not point to underlying joint disease. Baker's cysts arise between the tendons of the medial head of the gastrocnemius
Gastrocnemius muscle
In humans, the gastrocnemius muscle is a very powerful superficial pennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle...
and the semimembranosus muscle
Semimembranosus muscle
The semimembranosus is a muscle in the back of the thigh. It is the most medial of the three hamstring muscles.-Structure:The semimembranosus, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh....
s. They are posterior to the medial femoral condyle
Medial condyle of femur
The medial condyle is one of the two projections on the lower extremity of femur.The medial condyle is larger than the lateral condyle due to more weight bearing caused by the center of gravity being medial to the knee. On the posterior surface of the condyle the linea aspera turns into the...
.
The synovial
Synovium
Synovial membrane is the soft tissue found between the articular capsule and the joint cavity of synovial joints....
sac of the knee joint can, under certain circumstances, produce a posterior bulge, into the popliteal space
Popliteal fossa
The popliteal fossa is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia.-Boundaries:The boundaries of the fossa are:-Roof:...
, the space behind the knee. When this bulge becomes large enough, it becomes palpable and cystic. Most Baker's cysts maintain this direct communication with the synovial
Synovial joint
A Synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in the body of a mammal. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones....
cavity of the knee, but sometimes, the new cyst pinches off. A Baker's cyst can rupture and produce acute pain behind the knee and in the calf and swelling of the calf muscles
Triceps surae
The triceps surae is a pair of muscles located at the calf - the gastrocnemius and the soleus...
.
Diagnosis is by examination. A baker's cyst is easier to see from behind with the patient standing with knees fully extended. It is most easily palpated (felt) with the knee partially flexed. Diagnosis is confirmed by ultrasonography
Medical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
, although if needed and there is no suspicion of a popliteal artery
Popliteal artery
In human anatomy, the popliteal artery is defined as the extension of the "superficial" femoral artery after passing through the adductor canal and adductor hiatus above the knee...
aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
then aspiration of synovial fluid from the cyst may be undertaken with care. An MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
image can reveal presence of a Baker's cyst.
A burst cyst can cause calf pain, swelling and redness that may mimic thrombophlebitis
Thrombophlebitis
Thrombophlebitis is phlebitis related to a thrombus . When it occurs repeatedly in different locations, it is known as "Thrombophlebitis migrans" or "migrating thrombophlebitis".-Signs and symptoms:...
or a potentially life-threatening deep vein thrombosis
Deep vein thrombosis
Deep vein thrombosis is the formation of a blood clot in a deep vein. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected...
(DVT) which may need to be excluded by urgent blood tests and ultrasonography. Although an infrequent occurrence, a Baker's cyst can compress vascular structures and cause leg edema and a true DVT.
Treatment
Baker's cysts usually require no treatment unless they are symptomatic. Often rest and leg elevation are all that is needed. If necessary, the cyst can be aspiratedAspirator (medical device)
A medical aspirator is a small suction machine used to remove mucus and other bodily fluids from a patient. These machines are often designed to be portable for use in ambulances and nursing homes, and can run on AC/DC or battery power. Major manufacturers include Allied Healthcare and Impact...
to reduce its size, then injected with a corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
to reduce inflammation. Surgical excision
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
is reserved for cysts that cause a great amount of discomfort to the patient. A ruptured cyst is treated with rest, leg elevation, and injection of a corticosteroid into the knee. Recently, prolotherapy
Prolotherapy
Prolotherapy is also known as "proliferation therapy" or "regenerative injection therapy." involves injecting an otherwise non-pharmacological and non-active irritant solution into the body, generally in the region of tendons or ligaments for the purpose of strengthening weakened connective tissue...
has shown encouraging results as an effective way to treat Baker's cysts and other types of musculoskeletal conditions.
Baker's cysts in children, unlike in older people, nearly always disappear with time, and rarely require excision.
Cryotherapy
Ice pack therapy may sometimes be effective way of controlling the pain caused by Baker's cyst. Ice must not be applied directly onto the skin but be separated by a thin cloth. Alternatively, cooling packs may be used, but the total application time for any product is for no more than 15 minutes at a time.Medication
Medications bought at pharmacies may be used to help soothe pain. Painkillers with paracetamolParacetamol
Paracetamol INN , or acetaminophen USAN , is a widely used over-the-counter analgesic and antipyretic . It is commonly used for the relief of headaches and other minor aches and pains and is a major ingredient in numerous cold and flu remedies...
, a.k.a. Tylenol
Tylenol
Tylenol is a North American brand of drugs advertised for reducing pain, reducing fever, and relieving the symptoms of allergies, cold, cough, and flu. The active ingredient of its original, flagship product, paracetamol , is marketed as an analgesic and antipyretic...
(c) (acetaminophen), or with the additional anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
action (such as ibuprofen
Ibuprofen
Ibuprofen is a nonsteroidal anti-inflammatory drug used for relief of symptoms of arthritis, fever, as an analgesic , especially where there is an inflammatory component, and dysmenorrhea....
or naproxen
Naproxen
Naproxen sodium is a nonsteroidal anti-inflammatory drug commonly used for the reduction of pain, fever, inflammation and stiffness caused by conditions such as:...
), may be used. Stronger non-steroidal anti-inflammatory drug
Non-steroidal anti-inflammatory drug
Nonsteroidal anti-inflammatory drugs, usually abbreviated to NSAIDs or NAIDs, but also referred to as nonsteroidal anti-inflammatory agents/analgesics or nonsteroidal Anti-inflammatory medicines , are drugs with analgesic and antipyretic effects and which have, in higher doses, anti-inflammatory...
s may be required by prescription
Medical prescription
A prescription is a health-care program implemented by a physician or other medical practitioner in the form of instructions that govern the plan of care for an individual patient. Prescriptions may include orders to be performed by a patient, caretaker, nurse, pharmacist or other therapist....
from one's general practitioner
General practitioner
A general practitioner is a medical practitioner who treats acute and chronic illnesses and provides preventive care and health education for all ages and both sexes. They have particular skills in treating people with multiple health issues and comorbidities...
.
Heat
Heat is also commonly used. The application of a heating padHeating pad
A heating pad is a pad used for warming of parts of the body in order to manage pain. Localized application of heat causes the blood vessels in that area to dilate, enhancing perfusion to the targeted tissue...
on a low setting for 10–20 minutes may relieve some pain, but only if instructions are followed carefully.
Bracing
A knee brace can offer support giving the feel of stability in the joint. If only support is necessary, a simple elastic bandage is recommended; however, braces compress the back of the knee, where it is most tender, and can cause pain.Rest and specific exercise
Many activities can put strain on the knee, and cause pain in the case of Baker's cyst. Avoiding activities such as squatting, kneeling, heavy lifting, climbing, and even running can help prevent pain. Despite this, some exercises can help relieve pain, and a physiotherapist may instruct on stretching and strengthening the quadriceps and/or the patellar ligamentPatellar ligament
The patellar ligament is the central portion of the common tendon of the Quadriceps femoris, which is continued from the patella to the tuberosity of the tibia.-Anatomy:It is a strong, flat, ligament, about 10 cm...
.