A paralabral cyst — also called a ganglion cyst — is a fluid-filled collection arising from the shoulder joint. Most cause no symptoms at all, and only matter when they press on nearby structures such as a nerve. So what is a paralabral cyst, and does it need treatment?

paralabral cyst shoulder on MRI

What is a paralabral cyst of the shoulder? 

A paralabral cyst is a small fluid collection just outside the shoulder joint. These cysts arise from tears of the labrum — the rim of cartilage that encircles the shoulder socket to make the joint more stable. When the labrum tears, joint fluid can escape through the tear and collect outside the joint, forming the cyst. The same kind of cyst occurs elsewhere in the body, such as the wrist or foot, where it’s called a ganglion.

So a paralabral cyst is really a marker of an underlying labral tear — which is an important part of understanding it.

What causes a paralabral cyst?

The most common cause is a labral tear — such as a SLAP tear (a tear at the top of the labrum). These tears follow trauma such as a shoulder dislocation, overuse in sport, or age-related wear. Fluid then escapes through the tear and pools, forming the cyst.

Symptoms of a shoulder paralabral cyst

Most paralabral cysts cause no symptoms. But a cyst that grows can press on nearby structures — and that’s when problems arise:

  • A cyst at the back of the shoulder (the spinoglenoid notch) can compress the suprascapular nerve, causing pain, weakness, and muscle wasting around the shoulder blade.
  • A cyst at the bottom of the joint can compress the axillary nerve — the picture of quadrilateral space syndrome — causing armpit pain and wasting of the deltoid.
  • The underlying labral tear can cause shoulder pain independently of the cyst.

A useful clue: pain from a cyst tends to be constant, and not made worse by movement — unlike many other shoulder problems. And if a cyst is compressing a nerve, there’s often visible muscle wasting.

One challenge is that this pain can be hard to distinguish from other causes — rotator cuff pain, frozen shoulder, or a pinched nerve in the neck — which is why an accurate diagnosis matters.

How is a paralabral cyst diagnosed?

Imaging makes the diagnosis:

  • MRI — shows the cyst clearly, whether it’s compressing a nerve, and any resulting muscle wasting (atrophy and fatty change). It also rules out other causes of shoulder pain.
  • Ultrasound — also shows the cyst and any muscle wasting, and it’s used to guide a needle for aspiration.

How is a paralabral cyst of the shoulder treated?

The most important principle: most paralabral cysts don’t need treatment. Most cysts found on MRI are incidental, and small cysts usually don’t cause pain. Treatment is reserved for larger cysts that press on nerves or other structures.

Where treatment is needed, we work from simple to more involved:

Aspiration (the usual first step)

paralabral cyst shoulder
aspiration of paralabral cyst

We try aspiration — draining the cyst — as the first-line procedure. It should always be done under ultrasound guidance by someone experienced in ultrasound procedures.

First, local anaesthetic numbs the skin and muscle over the cyst. A larger needle is then used to drain the cyst, which often contains a thick, gel-like fluid. A small dose of cortisone is added to the emptied sac to discourage it from refilling. Where the underlying labral tear is the main source of pain, we sometimes inject the joint itself. After the procedure, you rest the shoulder for about a week, then start rehabilitation with a physiotherapist.

Surgery

If simple treatment fails, keyhole surgery can repair the underlying labral tear and drain the cyst. The evidence shows this is effective in most cases, but it carries greater risk than aspiration — so it’s reserved for cysts that haven’t responded, particularly where a nerve is compressed.

Frequently asked questions about a paralabral cyst of the shoulder

Will a paralabral cyst go away on its own?

Sometimes. Cysts can change in size over time — some grow, while others shrink or disappear. A small, painless cyst can often be watched rather than treated.

Can a paralabral cyst be cancerous?

No. A paralabral cyst is a benign fluid collection with a distinct, recognisable appearance on ultrasound and MRI that’s quite different from a cancerous growth.

Do small paralabral cysts cause shoulder pain?

Usually not. Small cysts are typically painless and found incidentally. It’s the larger cysts that cause trouble by pressing on nerves or other structures. When someone with a small cyst has shoulder pain, that pain is usually coming from the underlying labral tear — or from something else entirely, such as tendonitis or a frozen shoulder — rather than the cyst itself.

What counts as a “large” paralabral cyst?

As a general guide, a cyst larger than about 2 cm is considered significant — that’s the size at which it’s more likely to press on a nerve or other structures and actually cause symptoms.

Should I have surgery to remove a small cyst?

Usually not, and it’s worth being cautious about surgery for a small cyst. Because small cysts rarely cause pain, removing one often doesn’t resolve the symptoms — which are more likely due to the labral tear or another cause. When the pain is due to the tear, a targeted joint injection is often the first appropriate option, with cyst aspiration added if the cyst is large or pressing on a nerve.

Is PRP useful for a paralabral cyst or labral tear?

Not especially. PRP tends to be less effective for labral tears, so it isn’t the first choice here. Treatment is usually aimed at the tear (a targeted injection) and, where needed, the cyst (aspiration) — with surgery reserved for cases that don’t respond.

Final word from Sport Doctor London about paralabral cysts

Paralabral cysts of the shoulder are common, and most cause no pain and need no treatment. Where a cyst is large or pressing on a nerve, treatment helps — and an ultrasound-guided aspiration, often combined with a targeted joint injection for the underlying labral tear, should always be tried before surgery. Because a small cyst is rarely the real source of pain, it’s worth being cautious about operating on one.

If you have shoulder pain and have been told you have a cyst, Dr Masci can assess you in London, including an in-clinic ultrasound. Contact the team here or call +44 (0) 203 488 0350. 

Other related shoulder conditions: