Parthian/Sassanid heavy cavalry use bamboo lances?

[Urselius]

Was it not the case that Byzantine cavalry were dual-armed and relied on mainly bow fire, whilst western cavalry lacked bows and relied on their initial charge breaking the enemy?

This was not the case by the late 11th century, when Byzantine heavy cavalry were dedicated lancers, they did not usually carry bows. Bows were employed by specialist horse archers usually recruited from steppe nomads, such as Cumans, Pechenegs and Uzes, from the Seljuk Turks or from peoples with nomad ancestry settled within the Empire such as the Vardariots and the Moglena Pechenegs.

Early in his military career Emperor Alexios I Komnenos countered Norman knights with his own kataphraktoi, but they were repeatedly broken and routed. Later on he used various stratagems aimed at avoiding direct contact between his heavy cavalry and Norman knights, reserving his heavy cavalry for counterattacks. During the reigns of his successors John II and Manuel I this disparity of effectiveness seems to have narrowed and disappeared, the only reasonable conclusion is that the Byzantines adopted the Western way of fighting in this period. This is confirmed by Manuel I organising jousts against Westerners, in which he personally excelled.

The couched lance technique was not merely tucking the lance shaft under the arm. If you think that the couched lance technique was in use from Antique times onwards then it really cocks up military history big time, as I have argued above . If Western Europeans had not evolved a new and very effective fighting technique for heavy cavalry in the latter half of the 11th century, then you need to do some quite disreputable logic chopping to account for historical facts.

Here a 13th century image of Richard I of England shows the characteristics of the full couched lance technique:

https://en.wikipedia.org/wiki/File:RichardSaladin.jpg

Note: the lance is supported for essentially all its length by one arm (large old lance head too!) and the shaft is right up, locked into the armpit, the legs are so straight they are almost depicted bending forwards, they are held pushed out to the front, the heel of the foot is lower than the toes. The cantle of the saddle is very tall and envelops the riders hips completely.