Most serious bondage injuries involve nerve damage. Bondage always involves some risk of nerve damage, so everyone who does bondage should understand the basics of how to avoid nerve injuries.
If you choose to engage in high-risk bondage, you must get expert training on nerve injuries before you start. This is just as true for bottoms as for riggers.
Nerve injuries are usually caused by rope putting pressure on a vulnerable nerve. The most serious nerve injuries can drastically reduce your ability to use your hand or arm for a period of several months, with significant lifelong impairment.
Circulation loss is fairly common in bondage. In an otherwise healthy person, it is fairly safe to leave an area red, swollen, and warm for up to 20 minutes. Bondage that makes an area cold, clammy, or pale should be removed immediately.
Some health conditions can make any amount of circulation loss dangerous. If you have diabetes, peripheral neuropathy, or any other chronic health condition, you should avoid any circulation loss unless your doctor tells you otherwise.
Most serious nerve injuries involve suspension bondage and/or a TK, which places rope over the radial nerve in the upper arm. These are both high-risk techniques that require substantial training to perform responsibly.
Nerve damage gets worse over time: quickly detecting and correcting a problem can make the difference between a minor nuisance and a serious injury.
Numbness can be caused by nerve damage (which is often serious) or circulation loss (which is often not serious). Because there is no reliable way to tell the difference, you should always treat numbness as an emergency.
If you sprain your knee repeatedly, you are likely to develop chronic knee problems. Similarly, repeated nerve injuries can cause cumulative damage. Be thoughtful about the long-term consequences of your choices.