What’s This Bump At The End Of My Finger? 5 Tips To Understanding Mucous Cysts
In this ‘Basics” article, I’d like to describe an extremely common finger cyst known as a mucous cyst.
As we age, the chances of developing a mucous cyst rise. This is because of their association with arthritis. There are a few critical facts to know about these cysts to keep your finger safe and keep you out of the hospital.
Let’s get you that information in under five minutes!
1. A mucous cyst is not dangerous, but it can be very painful
One of the first things I like to convey to a patient coming to me for a new problem is whether the issue is ‘dangerous’ or not. Most things in hand surgery are not, and this conveys a sense of ease to begin the appointment.
Especially in the case of something growing on your finger.
This holds true for a mucous cyst. These are not dangerous entities. BUT. They can be very painful!
2. Location is everything, but an x-ray confirms the diagnosis
So what is a mucous cyst?
Essentially, this is a collection of joint fluid that has escaped the joint. This is commonly seen in the wrist as a ganglion cyst (read about here), but when it occurs at the joint closest to your fingernail, we call it a mucous cyst.
These will be found over the back of the hand, typically quite close to the nail itself (see Figure 1).
Figure 1 - Mucous cyst between the fingernail and DIP joint
These cysts get a different name because they actually have a slightly different cause compared to a ganglion cyst. These are nearly always associated with arthritis (read more here) of the underlying joint. We call this joint the distal interphalangeal joint, or DIP, for short.
If arthritis develops in the DIP, it is common to develop osteophytes, otherwise known as bone spurs. A bone spur is your body’s natural response to developing arthritis.
In a mucous cyst, this bone spur can push its way out of the joint and create a thinning of the joint capsule. If joint fluid pushes into this space, a small mucous cyst will develop.
The joint will naturally continue to make more and more fluid, and the cyst will grow and grow. Eventually, it will be seen at the level of the skin. This can be very painful and irritating.
Because these are always associated with a bone spur, an x-ray will confirm the diagnosis. If you have a cyst near the DIP joint and an underlying bone spur at that location on an x-ray, then it’s a slam dunk. You officially have a mucous cyst.
3. If your mucous cyst starts draining fluid, I need to know about it right away
The reason I like to break things down into ‘dangerous’ and ‘not dangerous’ is to inform our treatment options.
With something ‘not dangerous’ like a mucous cyst, that typically means ‘doing nothing’ is an option. If it’s not that painful and it’s not causing you issues, then you can just keep an eye on it.
Within that context, there are a couple of important things to know about a mucous cyst.
The first is your nail. If these cysts get big and come close to the base of your nail, they can actually put pressure on the cells that grow your nail. You would notice this as a subtle groove forming and beginning to grow out in the nail itself.
If this goes on long enough, it can be permanent. If it bothers you, see a hand specialist about cyst removal. If it doesn’t, many would happily go on living with this small groove in the nail, especially when the alternative means a small surgery.
The other thing we must look out for is drainage. If the cyst comes to the surface and actually starts draining fluid, get to a hand specialist right away. Remember. These cysts connect directly to the joint and thus can cause a joint infection, which is a BIG DEAL. These require surgery, many weeks of at-home IV antibiotics…
4. Never. Ever. Let anybody drain your mucous cyst.
And this brings me to my next point.
Do not. Under any circumstances. Let anybody drain these!
That means you, your friend, your doctor. Nobody.
Draining a mucous cyst is not the way they are treated. In the best-case scenario, the cyst will come right back. As long as that bone spur is there, these cysts will return.
The worst-case scenario? After draining it, you’ve now exposed the depths of your joint directly to the outside world. Which means bacteria get in. Which means joint infection. Which means emergency room -> admission to the hospital for days -> surgery -> long-term IV antibiotics -> arthritis -> possibly permanent joint pain and stiffness.
I’ve seen it happen, and it is devastating.
It’s tempting to ‘just stick a needle in it.’ Don’t do it!
5. If you want it treated, (minor) surgery is the only option
As I alluded to above, surgery is the only way to get these cysts out safely and minimize the chances of recurrence. Albeit a minor surgery, but still surgery.
This can typically be done with you wide awake after numbing your finger. No additional anesthesia is needed.
A 1.5 cm incision is made over the cyst. The cyst is drained. I then open your joint (under sterile conditions!) and remove the bone spur that causes the cyst in the first place. Again - without removing the bone spur, the cyst will just come right back.
Recovery typically entails having 2-3 stitches removed about two weeks after the procedure. I ask my patients not to engage in heavy lifting or gripping that could pop open the wound during the first three weeks after surgery.
Typical daily use of the fingers is fine right away, even on the night of surgery (you will just be in a bandage from the procedure). After those first three weeks, as long as the wound is healed, you can do whatever you would like.
Wrapping Up
Did you learn something new?
Hopefully, you can take this new knowledge of your finger cyst and apply it where you need it. My ultimate goal is to empower you with the flexibility to stay out of my office if you don’t need to be here!
If something doesn’t seem right, or you would like to pursue cyst excision, I would be happy to walk you through the process and get you the treatment you need. If that’s the case, come see me in Denver, Colorado.
