not on MJ but I have seen shoots like that on White Oaks after I had pruned the small tree back, actually I cut the big tree down and never ground the stump out.
usually it will pick a branch to take over and it will become your new main stalk. I had a blueberry do it. It didn't effect yield or overall health of the plant.
Looks like an imbalance or overproduction of growth hormone. Definitely indicative of a response to tissue damage, as mentioned by several above. As long as she's happy and green I think it's cool. Almost like a bonsai!
all my lst mothers have that same bulbous formation, im sure its just the plants way of reinforcing a weakened portion of the stem where stress affected that particular area of that plant.