What Causes a Ganglion Cyst?
Ganglion cysts form when mucin "droplets" accumulate and coalesce in the soft tissues near joints, tendons, or ligaments, though the exact mechanism remains incompletely understood. 1
Pathophysiology of Formation
The current leading theory holds that extra-articular mucin droplets gather together to form the main cyst body, with the cyst wall and connecting pedicle (linking the cyst to a nearby synovial joint) developing only after the initial mucin accumulation. 1 This represents mucoid degeneration of the joint capsule, tendon, or tendon sheaths. 2
Anatomical Origins
Ganglion cysts develop from specific anatomical structures:
They arise from tendon sheaths, joints, and ligaments throughout the hand and upper extremity, as noted by the European League Against Rheumatism. 3
The most common locations are around the wrist and hand, though they can also occur in the knee, ankle, and feet. 3
Intra-articular ganglia are rare and can originate from structures like the anterior cruciate ligament, posterior cruciate ligament, or meniscus within joints. 4, 5
Intratendinous ganglion cysts are extremely rare, representing an unusual variant where the cyst forms within the tendon substance itself rather than adjacent to it. 2
Associated Factors
Trauma history may be present in some patients, though many cases occur without any identifiable precipitating event. 4, 5
The cysts contain fluid with a myxoid matrix that accumulates near tendons and joints. 4
Clinical Context
Approximately 50% of ganglion cysts will spontaneously resolve without intervention, indicating that whatever mechanism drives their formation can also reverse naturally in many cases. 1 This spontaneous resolution rate is important when counseling patients about observation versus active treatment.