A ganglion cyst is a fluid-filled lump that forms near a joint or tendon, most commonly on the wrist or hand. These cysts are the most common mass found on the hand and wrist, and they’re noncancerous. They range from pea-sized to about an inch across, sometimes appearing suddenly and sometimes growing slowly over weeks. While they can look alarming, many ganglion cysts are harmless and may eventually disappear on their own.
What’s Inside a Ganglion Cyst
The lump itself is a small sac filled with thick, jelly-like fluid. This fluid is mostly hyaluronic acid, the same substance your joints naturally produce for lubrication, along with smaller amounts of proteins. The gel-like consistency is why these cysts feel firm when you press on them, almost rubbery, even though they’re entirely liquid inside.
Unlike some other types of cysts, ganglion cysts don’t have a true lining of cells on their inner wall. This is an important distinction because it tells us something about how they form. Rather than being a pocket of tissue that fills with fluid, a ganglion cyst appears to develop when the connective tissue near a joint breaks down and creates a space that gradually fills with mucus-like material.
Where They Typically Appear
About 70% of ganglion cysts show up on the back (dorsal side) of the wrist. Another 20% form on the palm side of the wrist, and the remaining 10% develop along the tendon sheaths of the fingers, usually near the base of a finger. Less commonly, ganglion cysts can appear on the top of the foot, near the ankle, or around the knee.
Each location has a slightly different feel. Dorsal wrist cysts are usually the most visible and become more prominent when you bend your wrist forward. Volar wrist cysts sit near the base of the thumb and can press on nearby structures. Finger cysts tend to be small, sometimes only a few millimeters, but they can be surprisingly tender because there’s less padding in that area.
What Causes Them
The exact cause isn’t fully understood, but the leading theory points to degeneration of the connective tissue (collagen) around a joint. When that tissue breaks down, possibly from repetitive stress or minor injury, it creates small spaces that merge and fill with the thick mucin fluid. An older theory suggested that the joint lining herniates outward like a balloon, but this doesn’t hold up because ganglion cysts lack the cell lining you’d expect to see if that were the case.
Repetitive wrist motion, joint irritation, and prior injury to a ligament or tendon are all associated with cyst formation. Women develop ganglion cysts more often than men, in both adults and children. They can appear at any age, though they’re most common between ages 20 and 40.
Symptoms and What They Feel Like
Many ganglion cysts cause no symptoms at all beyond the visible lump. When they do cause problems, the most common complaint is a dull, aching pain that worsens with repetitive hand or wrist use. The cyst may press on a nearby nerve, causing tingling, numbness, or muscle weakness in the fingers. Some cysts change size over time, swelling with activity and shrinking with rest, which can be confusing if you’re trying to figure out what you’re dealing with.
The lump is typically smooth, round, and moves slightly under the skin when pushed. It feels firm but not rock-hard. If you notice a lump that’s very hard, doesn’t move at all, or is growing rapidly, that’s worth investigating further since those features are less typical of a ganglion cyst.
How They’re Diagnosed
Most ganglion cysts can be diagnosed with a physical exam alone. One classic bedside test involves shining a light directly against the lump in a darkened room. Because the cyst is filled with clear fluid, light passes through it and creates a bright glow. A solid tumor or blood-filled mass would block the light and appear dark. This simple transillumination test is often enough to confirm the diagnosis.
When there’s any uncertainty, ultrasound is the first-line imaging tool. On ultrasound, a ganglion cyst appears as a well-defined, dark (fluid-filled) structure, often with thin internal walls and a characteristic boost in the signal behind it. Fine internal echoes from the thick mucoid fluid are common. MRI is reserved for cases where the cyst is in an unusual location, when a deeper or hidden cyst is suspected, or when the diagnosis is unclear. On MRI, ganglion cysts appear bright on fluid-sensitive sequences and dark on other sequences, matching what you’d expect from a pocket of fluid.
Do They Go Away on Their Own
They can. In children followed for more than two years without treatment, 44% of ganglion cysts resolved completely on their own. Younger children (under 10) had even better odds, with spontaneous resolution reaching 53%, while children over 10 saw resolution about 35% of the time. Smaller studies in children have reported resolution rates as high as 83%.
In adults, spontaneous resolution also occurs but is studied less precisely. Because these cysts are benign and frequently painless, watchful waiting is a perfectly reasonable approach if the cyst isn’t bothering you. Many people live with a ganglion cyst for years. It may fluctuate in size, temporarily disappear, and then return.
Treatment Options
Aspiration
The simplest in-office procedure involves inserting a needle into the cyst and draining the thick fluid. It’s quick, relatively painless with local numbing, and provides immediate relief if the cyst was causing pressure or discomfort. The downside is a high recurrence rate. In one study of pediatric patients, only 18% of cysts treated with aspiration stayed resolved, which was actually worse than simply watching and waiting. The cyst tends to refill because the underlying sac remains intact. Some practitioners inject a steroid after draining to reduce the chance of recurrence, though evidence for this is mixed.
Surgical Removal
When a cyst keeps coming back, causes persistent pain, or interferes with hand function, surgical excision is the more definitive option. The surgeon removes the entire cyst along with a small portion of the joint capsule or tendon sheath where it’s attached, which reduces the chance of regrowth.
There are two approaches. Open surgery involves a small incision directly over the cyst. Arthroscopic surgery uses a tiny camera and instruments inserted through smaller incisions. Open excision has a recurrence rate of about 7%, while arthroscopic excision recurs closer to 17%. The tradeoff is that arthroscopic surgery generally means a smaller scar and potentially faster early recovery, but the higher recurrence rate is a meaningful difference. Recovery from either approach typically involves a few weeks of limited wrist use, with most people returning to full activity within four to six weeks.
Why You Shouldn’t Pop One at Home
The old folk remedy of smashing a ganglion cyst with a heavy book (sometimes called “Bible bumping”) is still surprisingly common advice. This is a bad idea. Even if the impact ruptures the cyst and temporarily flattens it, the fluid simply disperses into surrounding tissue and the cyst typically reforms.
The real danger is infection. A ganglion cyst has a direct connection to the joint. If the skin breaks during a home rupture attempt and bacteria get in, the infection has a short, open path straight into the joint space. A joint infection is a serious medical emergency that can cause lasting damage and requires aggressive treatment. The risk simply isn’t worth it for a condition that’s benign and has safe, effective treatment options available.