Are you saying that there is a sort of runner coming out from the main plant horizontally just above the ground, and then sending up a shoot? If this is what you meant, this is standard behavior for many bamboo, both runners and clumpers, especially when the plant has only been in the ground for a year or two. Don't worry...the bamboo knows what it's doing and you don't need to intervene.

Here is a new Textilis I have and if you look closely you can see that the shoots did not come up out of the soil, they grew out of the base of the older clums.

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This one is not my bamboo. But if you look at the base of the plant you can see how the new shoots develop from the lowest section of the older culms--they don't actually come breaking out of the ground.
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Here is a link that might be useful: garden photo blog