A Baker's cyst, also known as a popliteal cyst, is a benign swelling of
the semimembranosus 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. This is not a "true" cyst, 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 arthritis
or cartilage tear. Baker's cysts can also 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 muscles. 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
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
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.
An infrequent but potentially life-threatening complication, which may
need to be excluded by urgent blood tests and ultrasonography, is a deep
vein thrombosis. Quick assessment of the possibility of DVT may be required where
a Baker's cyst has compressed vascular structures, causing leg edema, as this
sets up conditions for a DVT to develop. A burst cyst commonly causes calf pain,
swelling and redness that may mimic thrombophlebitis.
Treatment Baker's cysts usually require no
treatment unless they are symptomatic. It is very rare that the symptoms are
actually coming from the cyst. In most cases, there is another disorder in the
knee tear, etc.) that is causing the problem. Initial treatment should be
directed at correcting the source of the increased fluid production. Often rest
and leg elevation are all that is needed. If necessary, the cyst can be
aspirated 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. CryotherapyIce pack therapy may
sometimes be effective way of controlling the pain caused by Baker's
cyst. Medication
Medications bought at pharmacies may be used to help soothe pain.
Heat Heat is also commonly used.
Bracing A knee brace can offer support giving
the feel of stability in the joint. 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 ligament.
References Notes
Bibliography Hellmann, DB. "Chapter 20: Arthritis &
Musculoskeletal Disorders". In Tierney LM, Jr., McPhee SJ, Papadakis MA.
Current Medical Diagnosis & Treatment. Philadelphia, PA: F. A. Davis Company.
ISBN 0-07-145323-7. Joint Healing.com-Baker's Cyst
External links Media related to Baker's cyst at
Wikimedia Commons Baker's cyst at GPnotebook
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