What is it about ?
An articular cyst (or synovial or arthro-synovial cyst) is a protrusion of the joint capsule or tendon sheath (envelope that surrounds a tendon), usually in the wrist. It contains a gelatinous fluid, which resembles the lubricant (synovial fluid or synovium) that is present in the joints and around the tendons.
We don’t know exactly why a joint cyst develops. A joint cyst that appears in the last joint of a finger is usually due toarthritis. Leakage in the joint capsule or tendon sheath is also a possible cause.
There is not necessarily a connection between the appearance of a joint cyst and a particular type of profession or hobby. A joint cyst can develop gradually or suddenly and goes away spontaneously 1 in 2 times.
In whom and how often does it occur?
The articular cyst affects 4.5 people in 1000. Each year, there are 3.3 new diagnoses of a joint cyst per 1000 people.
A joint cyst in the hand or wrist is more common in women between the ages of 20 and 40 and in people who have inflammation (arthritis) of the finger joints. People who have had a tendon injury also have a higher risk of developing a joint cyst.
How to recognize it?
An articular cyst looks like a small round or oval ball (nodule). Since it is filled with a gelatinous liquid, it is possible to press it down slightly. It is usually painless, but can cause a slight pain on the pressure when it gets bigger.
Joint cysts are usually found on the back of the wrist and in the palm of the hand, on the side of the thumb. But they can also appear near any joint or tendon.
Their dimensions vary from a few millimeters to several centimeters.
In some cases, the joint cyst compresses a nerve, which can cause pain, tingling, numbness and muscle weakness.
How is the diagnosis made?
The diagnosis is made on sight. The doctor will feel the mass. If it causes pain, the gelatinous fluid is drained from the cyst using a syringe (puncture). This allows the doctor to confirm the diagnosis. The gelatinous liquid is colorless and transparent. If the puncture fails, an ultrasound or a CT scan will be done.
What can you do ?
A joint cyst is harmless. In the absence of complaints, it is not necessary to deal with it. Do not try to pierce it or prick it with a needle. You risk damaging nearby structures. If the procedure is not performed under sterile conditions, you also increase the risk of infection.
In the case of a joint cyst in the foot, wearing suitable shoes can relieve the pressure.
What can your doctor do?
Joint cysts can only be treated when they cause complaints. The doctor will first try to empty the cyst with a syringe. Unfortunately, the effect is usually only short-lived. Every other time, the swelling comes back at some point.
Sometimes the doctor injects a small amount of cortisone inside the cyst. To date, however, there is not sufficient scientific evidence to support the effectiveness of this treatment. If necessary, the doctor can repeat the procedure several times.
If the joint cyst continues to recur, it can be removed with surgery. However, in 10 to 30% of cases, the cyst reappears thereafter.
Want to know more?
- Ultrasound here Where to find on this page of Cliniques St Luc UCL
- Scanner (CT-scan) – Erasme Hospital