Baker's cyst

Alternative names:

popliteal cyst

Definition:

An accumulation of joint fluid (synovial fluid) that forms in the tendon sheaths behind the knee.

Causes, incidence, and risk factors:

In children, the Baker's cyst appears as a painless swelling behind the knee that is more obvious with the knee fully extended. A large cyst may cause some discomfort or stiffness but generally is asymptomatic. Baker's cysts usually disappear spontaneously after several years.