Baker’s cyst in the knee or popliteal cyst is a sac in the posterior part of the knee. It usually occurs when the joint is filled with too much fluid. A soft-tissue thickening that develops and acts as protection against excessive fluid in the joint often appears with other intraarticular pathologies in the knee.
What causes Baker’s cyst in the knee?
When we talk about a swollen knee joint and thickening, specifically the back of the knee, we think of Baker’s cyst. It is a type of cyst that occurs as a result of irritation of the bursae. It appears in the popliteal cavity as a bulge in the joint capsule.
Internal disorders in the joint often affect the enlargement of the cyst. The cyst is in close connection with the joint. Irritation and effusion of the joint fluid into the cyst are caused due to pathologies in the joint (i.e., intraarticular pathologies). Menisci damage is most often the reason for appearance of the popliteal cyst.
The fluid in the joint appears for a variety of reasons. Excess fluid moves into the cyst, which reduces the detrimental effect of the elevated pressure in the knee joint.
The synovial fluid in the cyst only partially absorb through the semipermeable membrane. This causes high concentrations of fibrin, which forms a gelatinous substance.
It is a common occurrence in humans
Baker’s cyst is a fairly common pathology of the knee joint in children. Fortunately, it resolves spontaneously by the 20th month. In adults, however, it is different.
The appearance of popliteal cysts in the knee is strongly associated with effusion in the joint, with meniscus damage and degenerative changes in the knee (knee osteoarthritis). In addition, Baker’s cyst in the knee often occurs in people with:
- rheumatoid arthritis,
- systemic lupus erythematosus,
- patients with chronic renal failure,
Doctors check for the presence of cyst with the help of ultrasound diagnostics and magnetic resonance imaging.
Ultrasound examination of the Baker’s cyst is the best noninvasive imaging tests.
Baker’s cyst in the knee – symptoms
The clinical picture of Baker’s cyst manifests as a bulge on the back of the knee below the joint. In some people, the size of the cyst can cause pain and limit the full mobility of the knee joint.
In addition to swelling at the back of the knee, swelling around the entire joint and below can also occur. This is what usually causes the joint to harden and prevents the leg from fully flexing.
Most patients complain of constant pain during the day and stiffness of the knee.
Medical examination is necessary
The doctor should completely orthopedically examine the knee joint. It is the only way to determine possible muscle atrophy, thickening and deformation. Also, only in the abdominal position the Baker’s cyst is most visible – it stands out.
The doctor should also examine the knee thoroughly to determine the position of the cyst. It is important to eliminate the cyst position close to popliteal artery and the possibility of pseudothrombosis (swelling of the tibia due to a ruptured cyst).
In a certain percentage of people who suffer from major problems with Baker’s cyst, the cyst may also rupture and the contents spill into the soft muscles.
Do not hesitate with visiting your doctor
Depending on the symptoms (swollen knee and possibly tibial part), it is not always the case that Baker’s cyst is the one that causes the problems. It can also be another disease, such as:
- popliteal artery aneurysm
- benign or malignant tumors
- degenerative cyst of the medial meniscus
- musculoskeletal injury
In any event, never delay seeing a doctor.
Treatment of Baker’s (popliteal) cyst
Should you remove Baker’s cyst?
In principle, treatment of Baker’s cysts in the initial phase or when it is smaller and does not cause symptoms is not necessary. At that point, surgical procedures are out of question. In the younger population, there is even a high probability that they will disappear on their own.
The most important thing to be aware of is that Baker’s cyst is only the result of some other pathology in the knee joint. That is why it is first necessary to pay attention to the primary problem. The cyst itself is of secondary importance and requires special attention only in rare cases.
If symptoms occur, problems with Baker’s cyst are alleviated conservatively as follows:
- taking nonsteroidal anti-inflammatory drugs
- rest with elevated leg
- cooling the sore spot
- use of an elastic splint for the knee joint
- avoiding prolonged sitting and excessive strain on the knee joint
- performing therapeutic exercises to maintain or gain joint mobility
Some doctors also opt for the cyst puncture. It is supposed to act as a relief for the joint and pain in the short term. Other doctors also choose to add an injection of corticosteroids into the emptied cyst to prevent inflammation.
In rare cases, it is also necessary to remove Baker’s cyst – for example, if it causes extremely severe problems like deep vein thrombosis.