First, I'd recommend you look at the Levantia site - this is based upon a LOT of research by someone in a very good position to have access to original data. Look particularly at "kremasmata, Klivanion, Kavadion" article, and the reconstructions of Byzantine armour - Dr Tim Dawson takes the position that a lot of Byzantine limb protection seems to have been padding, but that there are also contemporary references and illustrations showing sleeve armour and armoured skirts made of "upside down lamellar".
There are also a lot of contemporary illustrations showing (particularly sleeve) armour made of some kind of flexible strips - commonly referred to as "pteruges" ("wings"), as shown at
http://www.geocities.com/egfroth1/Joshua1.jpg I've seen it theorised that they might be either leather or padded fabric. There are also similar ones which seem to be made of metal plates laced together (see
http://www.metmuseum.org/explore/byzant ... m_12a.html )
I'm currently working on a reconstruction of sleeve armour based on the sleeves and skirt shown at
http://www.culture.gr/2/21/218/218ci/00/l9-1.html . I'm hoping to work it all out and finish it in another month or so, and I'll post it when it's done.
As far as leg armour goes, you're looking at what are effectively greaves, usually of flexible or padded material, known as "toubia" or "kampotoubia" (a single one is called a "toubion") - they end below the knee. There seems to be no evidence of knee or upper leg armour at all. f you want to protect the knees and upper legs, you should hide the protection under the clothing. Cavalry wore boots - see Tim Dawson's Levantia site for some pics. Note that though I don't agree with all his conclusions, he's done what I regard as the best and most comprehensive research on the subject, and overall, makes a lot of sense.
The sleeves and skirt are not always used, either - they seemt o be a matter of "if you can, then have sleeves and skirt - otherwise just go with the chest armour"
Hope this helps. I'm happy to add to this at more length, if you want to email me off-list.