A Rear Riew
Not a pretty sight, but it does show how the Cuisses and Poleyns are strapped around the thigh.
 
Note the 'wings' of the Poleyns to protect the side and back of the knee.
 
The straps and buckles of the Greaves can be clearly seen on the inside of the leg in the upper picture.
 
Also note the 
Cuisses, Poleyns and Greaves
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Cuisses
Covered the thighs.  The inside of the leg is left exposed, this is because if riding, a knight needs to be able to sit on his horse. It is a weak point in the armour and shows how function still dictated how the armour was designed.  Cuisses often had Poleyns attached to them, which protected the knees (poleyns could also be worn on their own).
Poleyns
Fitted over the knees, these would have large side wings on to make sure that whether the knee was bent or straight that a sword could not cut the 'hamstring' - the tendons at the back of the knee - which completely debilitates the person.
Greaves
These fitted over the lower legs and had two types. The cheaper demi-grieves just covered the front of the lower leg like a footballers shin pad. Whereas fully enclosed grieves covered the calves as well, giving better all round protection but making them a difficult piece to make as each leg is a slightly different shape. An apprentice armourer would quite often have to make a pair for the master of a town's Guild of Armourers as his final examination.
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