Baker's cyst

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Baker's cyst
Other namesPopliteal cyst [1]
Ultrasound Scan ND 0125091859 0930540.png
Ultrasound image of Baker's cyst
Specialty Rheumatology   OOjs UI icon edit-ltr-progressive.svg
Symptoms None, swelling behind the knee, stiffness, pain [1] [2]
Complications Deep vein thrombosis, peripheral neuropathy, ischemia, compartment syndrome [2] [3]
Usual onsetGradual [1]
Risk factors Knee problems such as osteoarthritis, meniscal tears, rheumatoid arthritis [1] [3] [4]
Diagnostic method Confirmed by ultrasound or MRI [3]
Differential diagnosis Deep venous thrombosis, aneurysms, ganglion, tumors [1]
Treatment Supportive care, aspiration, surgery [1]
Frequencyc. 20% [2] [3]

A Baker's cyst, also known as a popliteal cyst, is a type of fluid collection behind the knee. [4] Often there are no symptoms. [2] If symptoms do occur these may include swelling and pain behind the knee, or knee stiffness. [1] If the cyst breaks open, pain may significantly increase with swelling of the calf. [1] Rarely complications such as deep vein thrombosis, peripheral neuropathy, ischemia, or compartment syndrome may occur. [2] [3]


Risk factors include other knee problems such as osteoarthritis, meniscal tears, or rheumatoid arthritis. [1] [3] [4] The underlying mechanism involves the flow of synovial fluid from the knee joint to the gastrocnemio-semimembranosus bursa, resulting in its expansion. [1] The diagnosis may be confirmed with ultrasound or magnetic resonance imaging (MRI). [3]

Treatment is initially with supportive care. [1] If this is not effective aspiration and steroid injection or surgical removal may be carried out. [1] Around 20% of people have a Baker's cyst. [2] [3] They occur most commonly in those 35 to 70 years old. [4] It is named after the surgeon who first described it, William Morrant Baker (1838–1896). [5]

Signs and symptoms

Symptoms may include swelling behind the knee, stiffness, and pain. [1] If the cyst breaks open, pain may increase, and there may be swelling of the calf. [1] Rupture of a Baker's cyst may also cause bruising below the medial malleolus of the ankle (Crescent sign).


In adults, Baker's cysts usually arise from almost any form of knee arthritis (e.g., rheumatoid arthritis) or 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 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.

An infrequent but potentially life-threatening complication, which may need to be excluded by blood tests and ultrasonography, is a 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 thrombophlebitis.


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 (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 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.

Baker's cysts in children, unlike in older people, nearly always disappear with time, and rarely require excision.[ citation needed ]

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


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.[ citation needed ]

Related Research Articles

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Bursitis Human disease

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Popliteal artery Continuation of the femoral artery that supplies the lower leg

The popliteal artery is a deeply placed continuation of the femoral artery opening in the distal portion of the adductor magnus muscle. It courses through the popliteal fossa and ends at the lower border of the popliteus muscle, where it branches into the anterior and posterior tibial arteries.

Achilles tendinitis Medical condition

Achilles tendinitis, also known as achilles tendinopathy, occurs when the Achilles tendon, found at the back of the ankle, becomes sore. Achilles tendinopathy is accompanied by alterations in the tendon’s structure and mechanical properties. The most common symptoms are pain and swelling around the affected tendon. The pain is typically worse at the start of exercise and decreases thereafter. Stiffness of the ankle may also be present. Onset is generally gradual.

Shin splints Medical condition

A shin splint, also known as medial tibial hematoma, is pain along the inside edge of the shinbone (tibia) due to inflammation of tissue in the area. Generally this is between the middle of the lower leg to the ankle. The pain may be dull or sharp, and is generally brought on by high-impact exercise that overloads the tibia. It generally resolves during periods of rest. Complications may include stress fractures.

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Chondromalacia patellae is an inflammation of the underside of the patella and softening of the cartilage.

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Plantaris muscle One of the superficial muscles of the superficial posterior compartment of the leg,

The plantaris is one of the superficial muscles of the superficial posterior compartment of the leg, one of the fascial compartments of the leg.

The knee examination, in medicine and physiotherapy, is performed as part of a physical examination, or when a patient presents with knee pain or a history that suggests a pathology of the knee joint.

Knee effusion Medical condition

Knee effusion occurs when excess synovial fluid accumulates in or around the knee joint. It has many common causes, including arthritis, injury to the ligaments or meniscus, or fluid collecting in the bursa, a condition known as prepatellar bursitis.

Popliteal artery entrapment syndrome Medical condition

The popliteal artery entrapment syndrome is a rather uncommon pathology, which results in claudication and chronic leg ischemia. The popliteal artery may be compressed behind the knee, due to congenital deformity of the muscles or tendon insertions of the popliteal fossa. This repetitive trauma may result in stenotic artery degeneration, complete artery occlusion or even formation of an aneurysm.

Unhappy triad Medical condition

The unhappy triad, also known as a blown knee among other names, is an injury to the anterior cruciate ligament, medial collateral ligament, and meniscus. Analysis during the 1990s indicated that this 'classic' O'Donoghue triad is actually an unusual clinical entity among athletes with knee injuries. Some authors mistakenly believe that in this type of injury, "combined anterior cruciate and medial collateral ligament disruptions that were incurred during athletic endeavors" always present with concomitant medial meniscus injury. However, the 1990 analysis showed that lateral meniscus tears are more common than medial meniscus tears in conjunction with sprains of the ACL.

Knee bursae

The knee bursae are the fluid-filled sacs and synovial pockets that surround and sometimes communicate with the knee joint cavity. The bursae are thin-walled, and filled with synovial fluid. They represent the weak point of the joint, but also provide enlargements to the joint space. They can be grouped into either communicating and non-communicating bursae or, after their location – frontal, lateral, or medial.

Tear of meniscus Rupturing of the fibrocartilage strips in the knee called menisci

A tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. Menisci can be torn during innocuous activities such as walking or squatting. They can also be torn by traumatic force encountered in sports or other forms of physical exertion. The traumatic action is most often a twisting movement at the knee while the leg is bent. In older adults, the meniscus can be damaged following prolonged 'wear and tear'. Especially acute injuries can lead to displaced tears which can cause mechanical symptoms such as clicking, catching, or locking during motion of the joint. The joint will be in pain when in use, but when there is no load, the pain goes away.

Discoid meniscus

Discoid meniscus is a rare human anatomic variant that usually affects the lateral meniscus of the knee. Usually a person with this anomaly has no complaints; however, it may present as pain, swelling, or a snapping sound heard from the affected knee. Strong suggestive findings on magnetic resonance imaging includes a thickened meniscal body seen on more than two contiguous sagittal slices.

Pseudothrombophlebitis is a clinical condition where there are signs and symptoms of phlebitis in the absence of a thrombophlebitis lesion. Symptoms include pain, swelling, erythema and tenderness evolving over hours or days. It is often associated with the rupture or dissection of a popliteal cyst otherwise known as a Baker's cyst, although it can be associated with other disorders such as the arthritides. It may also occur as an orthopaedic surgical complication, secondary to trauma or as a presentation of septic arthritis. It is crucial to differentiate this condition from deep vein thrombosis as the treatment for DVT can cause adverse effects in patients with pseudothrombophlebitis.

Knee pain Medical condition

Knee pain is pain in or around the knee.


  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Hubbard, MJ; Hildebrand, BA; Battafarano, MM; Battafarano, DF (June 2018). "Common Soft Tissue Musculoskeletal Pain Disorders". Primary Care. 45 (2): 289–303. doi:10.1016/j.pop.2018.02.006. PMID   29759125.
  2. 1 2 3 4 5 6 Ferri, Fred F. (2015). Ferri's Clinical Advisor 2016 E-Book: 5 Books in 1. Elsevier Health Sciences. p. 200. ISBN   9780323378222.
  3. 1 2 3 4 5 6 7 8 Herman, AM; Marzo, JM (August 2014). "Popliteal cysts: a current review". Orthopedics. 37 (8): e678-84. doi:10.3928/01477447-20140728-52. PMID   25102502. S2CID   35470933.
  4. 1 2 3 4 Foris, LA; Bhimji, SS (January 2018). "Cyst, Baker". PMID   28613525.Cite journal requires |journal= (help)
  5. "William Morrant Baker". Who Named It.

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