Emergency room doctors have noticed a trend in the last ten years or so of people coming in with grisly injuries to their non-dominant hand, often requiring delicate surgery to repair tendons, nerves, and pulleys. These injuries were incurred in the process of cutting an avocado, leading to the term "Avocado Hand."
The overwhelming majority of injuries occurred when attempting to remove the avocado's large, hard seed, called a "stone".
"All patients reported that they had pressed the knife tip down perpendicularly onto the avocado seed and that it slipped off it and plunged into their hand," the doctors wrote.
And the injuries were not at all minor.
Prevention is a matter of learning how to cut an avocado without cutting yourself. Along with a description of the injuries, there's a step-by-step tutorial on avocado preparation at Real Clear Science.