Cuisses are defences for the upper leg. Sometimes refered to a thigh guards or thigh plates in modern parlance.
They developed from gamboised cuisses, which were sometimes worn over chausses at the beginning of the 14th century. They became more common as the century progresed to be replaced with a coat of plates style defence for the thigh in approximately 1340, and then replaced again somewhere in the middle of the century with plate. By the last quarter of the 14th century the cuisse had developed a single front plate with hinged back section and was articulated with a lame to the poleyn.