View source for Medicine:Baker's cyst

{{Infobox medical condition (new)
| name            = Baker's cyst
| synonyms        = Popliteal cyst<ref name=Hub2018/>
| image           = Ultrasound Scan ND 0125091859 0930540.png
| caption         = Ultrasound image of Baker's cyst
| pronounce       = 
| field           = 
| symptoms        = None, swelling behind the knee, stiffness, pain<ref name=Hub2018/><ref name=Fer2016/>
| complications   = [[Medicine:Deep vein thrombosis|Deep vein thrombosis]], [[Medicine:Peripheral neuropathy|peripheral neuropathy]], [[Medicine:Ischemia|ischemia]], [[Medicine:Compartment syndrome|compartment syndrome]]<ref name=Fer2016/><ref name=Her2014/>
| onset           = Gradual<ref name=Hub2018/>
| duration        = 
| types           = 
| causes          = 
| risks           = Knee problems such as [[Medicine:Osteoarthritis|osteoarthritis]], meniscal tears, [[Medicine:Rheumatoid arthritis|rheumatoid arthritis]]<ref name=Hub2018/><ref name=Her2014/><ref name=For2017/>
| diagnosis       = Confirmed by [[Physics:Ultrasound|ultrasound]] or MRI<ref name=Her2014/>
| differential    = Deep venous thrombosis, aneurysms, [[Biology:Ganglion|ganglion]], [[Medicine:Tumors|tumors]]<ref name=Hub2018/>
| prevention      = 
| treatment       = Supportive care, [[Medicine:Suction|aspiration]], surgery<ref name=Hub2018/>
| medication      = 
| prognosis       = 
| frequency       = c. 20%<ref name=Fer2016/><ref name=Her2014/>
| deaths          = 
}}
<!-- Definition and symptoms -->
A '''Baker's cyst''', also known as a '''popliteal cyst''', is a type of fluid collection behind the knee.<ref name=For2017>{{cite journal |last1=Foris |first1=LA |last2=Bhimji |first2=SS |title=Cyst, Baker |date=January 2018 |pmid=28613525}}</ref> Often there are no symptoms.<ref name=Fer2016/> If symptoms do occur these may include swelling and pain behind the knee, or knee stiffness.<ref name=Hub2018>{{cite journal |last1=Hubbard |first1=MJ |last2=Hildebrand |first2=BA |last3=Battafarano |first3=MM |last4=Battafarano |first4=DF |title=Common Soft Tissue Musculoskeletal Pain Disorders. |journal=Primary Care |date=June 2018 |volume=45 |issue=2 |pages=289–303 |doi=10.1016/j.pop.2018.02.006 |pmid=29759125|s2cid=46886582 }}</ref> If the cyst breaks open, pain may significantly increase with swelling of the calf.<ref name=Hub2018/> Rarely complications such as [[Medicine:Deep vein thrombosis|deep vein thrombosis]], [[Medicine:Peripheral neuropathy|peripheral neuropathy]], [[Medicine:Ischemia|ischemia]], or [[Medicine:Compartment syndrome|compartment syndrome]] may occur.<ref name=Fer2016/><ref name=Her2014/>

<!-- Cause and diagnosis -->
Risk factors include other knee problems such as [[Medicine:Osteoarthritis|osteoarthritis]], meniscal tears, or [[Medicine:Rheumatoid arthritis|rheumatoid arthritis]].<ref name=Hub2018/><ref name=Her2014>{{cite journal |last1=Herman |first1=AM |last2=Marzo |first2=JM |s2cid=35470933 |title=Popliteal cysts: a current review. |journal=Orthopedics |date=August 2014 |volume=37 |issue=8 |pages=e678-84 |doi=10.3928/01477447-20140728-52 |pmid=25102502}}</ref><ref name=For2017/> The underlying mechanism involves the flow of [[Biology:Synovial fluid|synovial fluid]] from the knee joint to the gastrocnemio-semimembranosus bursa, resulting in its expansion.<ref name=Hub2018/> The diagnosis may be confirmed with [[Physics:Ultrasound|ultrasound]] or [[Physics:Magnetic resonance imaging|magnetic resonance imaging]] (MRI).<ref name=Her2014/>

<!-- Treatment and history -->
Treatment is initially with supportive care.<ref name=Hub2018/> If this is not effective [[Medicine:Suction|aspiration]] and [[Biology:Corticosteroid|steroid]] injection or surgical removal may be carried out.<ref name=Hub2018/> Around 20% of people have a Baker's cyst.<ref name=Fer2016>{{cite book |last1=Ferri |first1=Fred F. |title=Ferri's Clinical Advisor 2016 E-Book: 5 Books in 1 |date=2015 |publisher=Elsevier Health Sciences |isbn=9780323378222 |page=200 |url=https://books.google.com/books?id=bbLSCQAAQBAJ&pg=PA200 |language=en}}</ref><ref name=Her2014/> They occur most commonly in those 35 to 70 years old.<ref name=For2017/> It is named after the surgeon who first described it, William Morrant Baker (1838–1896).<ref>{{cite web | title=William Morrant Baker | url=http://www.whonamedit.com/doctor.cfm/649.html | publisher=Who Named It}}</ref>

==Signs and symptoms==
Symptoms may include swelling behind the knee, stiffness, and pain.<ref name=Hub2018/> If the cyst breaks open, pain may increase, and there may be swelling of the calf.<ref name=Hub2018/> Rupture of a Baker's cyst may also cause [[Medicine:Ecchymosis|bruising]] below the medial malleolus of the ankle (Crescent sign).

==Cause==

In adults, Baker's cysts usually arise from almost any form of knee [[Medicine:Arthritis|arthritis]] (e.g., [[Medicine:Rheumatoid arthritis|rheumatoid arthritis]]) or [[Biology:Cartilage|cartilage]] (particularly a meniscus) tear.   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 (felt) with the knee partially flexed. Diagnosis is confirmed by ultrasonography, although if needed and there is no suspicion of a popliteal artery [[Medicine:Aneurysm|aneurysm]] then aspiration of synovial fluid from the cyst may be undertaken with care. An [[Physics:Magnetic resonance imaging|MRI]] image can reveal presence of a Baker's cyst.

An infrequent but potentially life-threatening complication, which may need to be excluded by blood tests and ultrasonography, is a [[Medicine:Deep vein thrombosis|deep vein thrombosis]] (DVT).  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 [[Medicine:Thrombophlebitis|thrombophlebitis]].

<gallery class="center" widths="225px" heights="250px">
Popliteal Cyst in situ.jpg|A specimen from a cadaver of a Baker's cyst in popliteal space
Image:Bakerzyste MRT ax.jpg|Baker's cyst on axial MRI with communicating channel between the semimembranosus muscle and the medial head of the gastrocnemius muscle.
Image:Bakerzyste1 MRT sag.jpg|Baker's cyst on MRI, sagittal image
Image:Bakerzyste2 MRT sag.jpg|Baker's cyst on MRI, sagittal image
</gallery>

==Treatment==
Baker's cysts usually require no treatment unless they are symptomatic.<ref>{{cite web |url=https://www.physio-pedia.com/Baker%27s_Cyst |title = Baker's Cyst - Physiopedia}}</ref> It is very rare that the symptoms are actually coming from the cyst.  In most cases, there is another disorder in the knee (arthritis, meniscal (cartilage) 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 [[Medicine:Aspirator (medical device)|aspirated]] to reduce its size, then injected with a [[Biology:Corticosteroid|corticosteroid]] to reduce inflammation. [[Medicine:Surgery|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.

Baker's cysts in children, unlike in older people, nearly always disappear with time, and rarely require excision.{{citation needed|date=May 2013}}

Ice pack therapy may sometimes be an effective way of controlling the pain related to Baker's cyst.{{citation needed|date=May 2013}} Heat is also commonly used.{{citation needed|date=May 2013}} A knee brace can offer support giving the feeling of stability in the joint.{{citation needed|date=May 2013}}

===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 hamstring stretching to reduce pressure on the Baker's Cyst, and strengthening exercises for the quadriceps and/or the patellar ligament.<ref>{{cite web | url=https://www.knee-pain-explained.com/bakers-cyst.html | title=Bakers Cyst: Causes & Treatment - Knee Pain Explained }}</ref>

==References==
{{Reflist}}

== External links ==


{{Medical resources
|  ICD10           = {{ICD10|M|71|2|m|70}}  
|  ICD9            = {{ICD9|727.51}}  
|  ICDO            =  
|  OMIM            =  
|  OMIM_mult       =  
|  MedlinePlus     = 001222  
|  eMedicineSubj   = radio  
|  eMedicineTopic  = 72  
|  DiseasesDB      = 1224  
|  MeshID          = D011151 
}}

{{Soft tissue disorders|state=collapsed}}

[[Category:Wikipedia medicine articles ready to translate]]

{{Sourceattribution|Baker's cyst}}