The synovial bursa serves as protection between the bones, consisting of a membrane of elastic fibres and fats enveloping the synovial fluid. This pocket reduces friction in the joints, such as the grease inside a bearing. The effusion of this pocket is a known problem for runners and triathletes.

Possible cases

A lack of synovial fluid inside the pocket increases friction inside the joint, promotes cartilage wear and, in the longer term, the development of osteoarthritis. On the other hand, too much fluid causes swelling that reduces the possible range of joint movement. As a result of the swelling, internal tensions appear and give birth to pain. In extreme cases, the synovial membrane can even rupture. Without getting to that point, they are nevertheless incapacitating in the practice of sport.


Birth of the Synovian effusion

The knee (the triathlete’s Achilles heel) is the part of the body most prone to synovial effusion. During physical activity as soon as you warm up, your body protects itself and secretes small amounts of liquid in anticipation of friction. These secretions are absorbed as the effort progresses. A dysfunction of the mechanism can prevent the resorption of the liquid and lead to synovial effusion.



The main causes of effusion in athletes are shocks and traumas. A fracture or sprain can cause joint complications even several months after the date of the incident. Synovial effusion will often be a mixture of blood and synovial fluid (hemarthrosis).

For a more distant post-traumatic effusion, it will be a purely liquid effusion.

Natural wear and tear due to sport can also cause effusion. Especially in the knee area, an effusion can be confused with tendonitis (wiper syndrome).


What to do about it?

The general good reflex to apply cold to the wound is also valid here, the cold reduces the swelling that causes the partial immobilization of the joint.

Anti-inflammatory drugs can also have the same role while limiting pain.

Light rotating massages on the bursa can also help resorption.

The consultation of a doctor is recommended in some rare cases the effusion may be related to a cyst, it can also become infected in some cases.

As rest is often the main factor in healing, the overinflated bursa will gradually disgorge. In the event that the bursa does not deflate itself, a puncture may be considered by a health professional.

Poncin Charles EF.