Synovial Cyst: Symptoms, Causes, Types & Treatment

Updated in March 2024

A synovial cyst is a fluid-filled sac that appears close to a joint. They are most commonly seen near the foot, wrist or knee. This type of cyst is filled with synovial fluid and is usually caused by direct injuries, stress injuries, or a joint defect.

The most common sign of a synovial cyst is the appearance of a round, soft lump that appears near the joint. This cyst does not typically cause any pain. However, because it grows close to muscles and tendons, some people may experience tingling, or a loss of strength or sensation, especially when the cyst is very large.

It is common for cysts to change size, and they may disappear naturally or reappear after treatment.

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Common symptoms

The main sign of a synovial cyst is the appearance of a soft lump with a diameter of about 3 cm near a joint. However, other symptoms may also emerge, such as:

  • Pain near the joint
  • Constant tingling in the affected limb
  • Lack of strength in the affected joint
  • Decreased sensitivity in the affected area

Normally, the cyst grows slowly over time, due to the accumulation of synovial fluid in the joint. These symptoms can also appear suddenly, which is more typical to happen following a direct blow.

There may also be very small synovial cysts that cannot be seen through the skin, but are very close to nerves or tendons. In this case, pain may be the only symptom, and the cyst is only discovered through imaging tests.

Possible causes

Synovial cysts tend to form due to the exit"of synovial fluid from the joint. The causes that lead to this fluid output are not yet very well understood, however it is believed that it may be associated with repetitive movements or frequent small injuries in the same location. It is also possible that they can occur due to blows, changes in the joint or the use of inappropriate footwear, in the case of a synovial cyst on the foot.

Types of synovial cyst

The most common synovial cysts are:

  • Synovial cyst on the foot: its causes include tendinitis and running with inadequate footwear. Treatment can be done through aspiration to drain the cyst or surgery, depending on the severity.
  • Synovial cyst of the knee, or Baker's cyst: most common on the back of the knee and the most recommended treatment may be aspiration for drainage followed by physiotherapy. 
  • Synovial cyst in the hand or wrist: it can appear in the hand, fingers or wrist and treatment may involve compression with a splint for immobilization, fluid aspiration, physiotherapy or surgery.

Synovial cysts can appear at any age and are diagnosed through physical examination, ultrasound or MRI.

Treatment options

Treatment for a synovial cyst depends on its size of the cyst and the presenting symptoms. If no symptoms are experienced, interventions with medication or surgery may not be necessary, as the cyst often ends up disappearing on its own.

If the cyst is large or causes pain or reduced strength, the doctor may prescribe anti-inflammatory medications, such as ibuprofen or diclofenac.

Aspiration of the fluid from the cyst can also be used as a form of treatment. This is done using a needle in the doctor's office under local anesthesia. After aspiration, a corticosteroid solution may be injected to help heal the cyst.

Natural treatment

An excellent home treatment to relieve synovial cyst symptoms is to apply ice to the affected area for about 10 to 15 minutes, several times a day.

Acupuncture can also be used to help treat synovial cysts, mainly to relieve local pain.

When surgery is necessary

Synovial cyst surgery is performed when the use of medication or aspiration has not resulted in any improvement in symptoms. Surgery is generally performed under local or general anesthesia, depending on the location of the synovial cyst, and consists of complete removal of the cyst.

After surgery, the person is usually discharged the same day and must rest for at least 1 week to prevent the cyst from appearing again. The doctor may also recommend two to four months of physiotherapy sessions to help with complete recovery.

Synovial cyst physiotherapy may involve ultrasound techniques, stretching, compression or active or resistance exercises to reduce inflammation and facilitate the natural drainage of the cyst. Physiotherapy must be individualized and is very important for the patient's recovery after surgery