Armor Type:  Knee armor

Brief Description:  A poleyn (or genouillère) is a critical piece of medieval plate armor designed to protect the vulnerable knee joint. Emerging around 1230, it shielded the kneecap (patella) from blunt trauma, slashes, and thrusts while utilizing articulated lames and side wings to maintain leg flexibility during combat. The design evolved significantly from the 13th to the 17th centuries, adapting to the progression of plate armor.

Early Evolution: The earliest forms were simple, boiled leather or steel caps strapped over mail chausses.

The "Fan" Plate: By the 14th century, poleyns often featured flared side plates, known as "fans" or gardes-de-genou, which deflected weapons away from the unprotected gap at the side of the knee.

Articulation: In 15th-century full plate harnesses, poleyns were seamlessly integrated between the upper thigh armor (cuisses) and lower leg armor (greaves or schynbalds) using overlapping, riveted sliding rivets (lames).

Regional Styles: Elaborate styles developed later, such as the fluted steel edges of the German Gothic style or the smooth, rounded surfaces of the Italian style.