Swelling protruding from a tendon sheath or joint capsule which has herniated escape of synovial fluid forms an encapsulated cyst.
Unknown - could be due to a weakness in tendon sheath or joint capsule.
More common on dorsum of foot.
Swelling is usually adjacent to an underlying joint or tendon sheath – the swelling may be hard or soft and fluctuant.
They may be painful and interfere with function
Skin can be moved over the ganglion, but the ganglion is firmly fixed to the underlying structure.
Usually asymptomatic, so can be left.
If symptomatic use padding or modify footwear or surgical removal