No, trust me. You guys are the idiots here. There's almost no heroin in the North East. What you're probably thinking of is hash. It looks similar, but heroin will have a sweeter taste if you taste it with the tip of your tongue. If you see people injecting, it's probably insulin. Marihuana addicts have compulsions to eat and so this has led to a very large obesity epidemic in certain segments of the population. This leads to late-onset diabetes (or Diabetes Simplex 1uz9). These people aren't born diabetics, but they pick it up from other potheads as they gather for so-called "Dream Sessions" where enormous amounts of cannabis are consumed (often exceeding the LD150 mark) and then chocolatey foods are consumed. This is why marihuana addicts are often associated in the North East with brownies and fudge. Chocolate has natural GABA-inhibiting functions as well as caffeine and trace quantities of harmaline (also found in Ayahuasca vines if you read your Carlos Castaneda...) This induces a trance-like state for the "Dreamer" and simultaneously destroys the kidneys - i.e. the main producers of endogenous insulin in humans. That's why you may be seeing drug-users with needles in their arms in the NorthEast that aren't actually heroin users.
This idea that "elbows" means marihuana is laughable.
Let me be quite clear: YOU DON'T INJECT MARIHUANA INTO YOUR VEINS.
I hope to fuck you guys are meta-trolling here...
Marihuana may be smoked, snorted, or used in a poultice and absorbed through the skin. Yes you could probably absorb marihuana through the skin at the elbow if you were so inclined. The active oils of cannabis are highly volatile and will pass through the cell-wall and into the thylakoid stacks of your blood vessels readily. Despite this, however, it is NEVER USED at the elbow as this would interfere with the use of the arm and with such high rate of absorption, the marihuana user will be compelled to seek food within minutes, making a poultice placed at the elbow a true inconvenience.