Cuisses are armor for the thighs.
Gamboised (quilted) cuisses offer padding for the upper leg. They also provide arming points for tying on poleyns, greaves, and such.
Over them I wear splinted leather outer cuisses, which are tied onto the gamboised cuisses with points and laces at the hip and at the knee.
Many funeral brasses from the 14th Century show studs or rivets on the upper thighs that suggest splinted leather. This detail from the brass of Sir Hugh Hastyngs, dated 1347, is typical.
This is a picture of gamboised cuisses
taken from the Maciejowski Bible of 1250.
My gamboised cuisses are stuffed with rags, which is authentic. I made them from Period Patterns #101, "Medieval Military Garments."