A ganglion cyst is one of those bumps you sometimes see on people’s wrist. They start off small, but can grow to the size of a golf ball. Watching a lump grow larger is unnerving, but the good news is they are harmless and they don’t become cancerous. The problem comes if they get so big that you can’t do up your cuffs, or if they are beside a nerve which can lead to aching or pins and needles in the hand.

Sometimes people decide to take matters into their own hands. Back in 1743, the German anatomist Lorenz Heister (who invented the word tracheotomy) listed the treatment options for ganglia – wiping the lump with saliva; taking a bullet that had killed a wild animal (ideally a stag) and strapping it to the cyst; or even rubbing it with the hand of a dead man. No surprise to hear these treatments have fallen out of favour, but judging by some eye-watering videos on YouTube there is one intervention that plenty of people are still happy to try – hitting the ganglion very hard with a huge book. The ideal book for the task, apparently, is the Bible, hence the nickname for ganglia being “bible cysts” or “bible bumps”.

Even if you have a pain threshold high enough to be on the receiving end of a heavy book, there are good reasons not to do it. The first is that it could cause damage to the surrounding tissue. As well as bad bruising, you can end up breaking a bone, so it is not something most doctors recommend today.

Some might decide to take the risk, but evidence suggests another reason for avoiding this course of action. In 1972, a much-cited study in the world of ganglia reported on 543 people with ganglion cysts, mainly on the wrist. (Occasionally you find them on feet and they can form next to any joint in the body.) Some tried the bible-bashing method: at first the fluid dissipated and the bump reduced; but recurrence rates were between 22% and 64%.

Research into the physical make-up of ganglia shows us why. They contain a thick jelly-like liquid called synovial fluid. Usually this fluid lubricates the joints and tendons, but sometimes it escapes and builds up outside the joint. Curiously, the fluid taken from the cysts is thicker and contains slightly different chemicals from synovial fluid. This substance collects within a shell, but hammering the bump just disperses the fluid temporarily. It doesn’t get rid of the shell, and so eventually the fluid can accumulate again, resulting in a new bump.

No one knows exactly why the fluid leaks out of joints in the first place, but there are some plausible theories. The first is that repeated flexing of the joint allows synovial fluid to leak out, which then builds up in a sack, forming a cyst. This could explain anecdotal reports that weightlifters are particularly prone to developing ganglia. Or could injury cause this? The problem is that you would expect those with evidence of an injury to be more prone to recurrence after surgery, but in fact there appears to be no difference.

So, how should you deal with a ganglion? The good news is that 45% of ganglia disappear by themselves after six years, and after a decade more than half have gone. For this reason an Australian review of treatments concluded that if the patient is not in pain, the best approach is often simply to reassure them that the lump is not cancerous and then wait to see if it goes away.

But if it’s hurting you or you really want to be rid of it, then there are options. Not surprisingly, there are no randomised controlled trials of having it hammered with a Bible, but other treatments have been tested. The fluid can be removed with a needle or the whole ganglion including its shell removed surgically. There is only a 13% success rate after aspiration with a needle just once, but it can be repeated, and sometimes a steroid injection is given at the same time to improve the chances of success. After surgery the recurrence rate is far lower, but it takes longer to recover. A review of randomised controlled trials shows that there are more complications from this approach, such as damage to the nerves or blood vessels or the formation of scar tissue.

So sadly, for something that’s so common, there’s no perfect treatment. But hoping it goes away by itself might still be better than bashing it with a Bible.

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