Popliteal Cyst

Have you noticed a lump or uncomfortable swelling behind your knee, particularly when walking, bending or trying to straighten your leg?

Perhaps your knee feels unusually tight when getting up from a chair, climbing stairs or going for your usual walk. You may have even noticed a soft lump behind your knee that seems to become more prominent when standing.

If you've been diagnosed with a popliteal cyst, you'll know how frustrating it can be when something as simple as bending your knee becomes uncomfortable.

A popliteal cyst is a fluid-filled swelling that develops at the back of the knee, usually when excess fluid from within the knee joint collects in a small sac.

The good news is that many popliteal cysts improve without surgery. Understanding what's causing the fluid to accumulate, which activities may be aggravating your knee and what treatment options are available can help you take the right steps towards recovery.

What Is a Popliteal Cyst?

A popliteal cyst, more commonly known as a Baker's cyst, is a fluid-filled swelling that develops in the hollow area at the back of your knee. The name popliteal simply refers to this anatomical region.

Your knee joint normally contains a small amount of lubricating fluid called synovial fluid. This fluid plays an important role in allowing the joint surfaces to move smoothly against each other, helping to reduce friction during movement. However, when your knee becomes irritated or inflamed, the joint may begin producing more synovial fluid than normal.

In some cases, this excess fluid passes into a small sac at the back of the knee, causing it to enlarge and form a noticeable swelling. This is what we call a popliteal cyst or Baker's cyst.

Depending on its size, the cyst may cause anything from mild tightness to considerable discomfort and difficulty bending the knee.

Importantly, a popliteal cyst can often be a symptom of another problem affecting the knee joint, rather than a completely separate condition. [1]

For a broader explanation, visit our Baker's Cyst Information page.

What Are the Symptoms of a Popliteal Cyst?

One of the more common symptoms is a feeling of tightness or fullness behind the knee.

You might notice that your knee feels relatively comfortable when resting, only to become increasingly uncomfortable when walking or bending your leg.

Common symptoms include:

• A lump behind the knee: A soft or firm swelling that may become more noticeable when standing or straightening the leg.

• Tightness behind the knee: A feeling of pressure or fullness, particularly when bending or straightening the leg.

• Pain or tenderness: Aching or discomfort around the back of the knee.

• Restricted knee movement: Difficulty bending or fully straightening the knee because of swelling or pressure.

• Pain after physical activity: Symptoms that become more noticeable after walking, exercising or standing for extended periods.

• Swelling around the knee: Sometimes accompanied by swelling within the knee joint itself.

Interestingly, not everyone with a popliteal cyst experiences pain. Smaller cysts may cause very few symptoms and are sometimes discovered during an examination for another knee problem.

However, larger cysts can become quite uncomfortable, particularly when they interfere with normal knee movement. [2]

What Causes a Popliteal Cyst?

In adults, popliteal cysts commonly develop when another condition causes irritation or inflammation within the knee joint. This can lead to increased production of synovial fluid, which may collect behind the knee.

Several underlying conditions can contribute.

Knee Osteoarthritis: Age-related changes and inflammation within the knee joint can result in excess synovial fluid, increasing the likelihood of a popliteal cyst developing.

Meniscus Injuries: A tear in the cartilage that cushions the knee joint can cause irritation and fluid accumulation.

Rheumatoid Arthritis: Inflammatory joint conditions can increase synovial fluid production and contribute to swelling.

Ligament Injuries: Injuries involving the structures that stabilise the knee may trigger inflammation and excess fluid production.

Other Knee Conditions: Gout and other inflammatory disorders may also contribute to the development of a cyst.

Sometimes, a popliteal cyst develops without an obvious underlying cause. However, when a cyst continues returning, it's particularly important to investigate whether an existing knee problem is contributing to the fluid accumulation.

Why Does a Popliteal Cyst Make Bending Your Knee Difficult?

One of the frustrating things about a popliteal cyst is the pressure it can create behind your knee.

Think about how often you bend your knees throughout the day. Getting into the car, sitting down, gardening, climbing stairs and even walking all involve repeated bending and straightening.

When a fluid-filled cyst develops behind the knee, these movements can place additional pressure on the surrounding tissues. As the cyst becomes larger, you may experience an increasingly uncomfortable feeling of tightness or fullness. You might find it difficult to bend your knee completely, or notice discomfort when trying to straighten your leg.

The important thing is to avoid repeatedly forcing your knee through movements that significantly aggravate the pain or swelling.

Temporarily modifying these activities while the underlying cause is investigated may help minimise further irritation.

Can a Popliteal Cyst Rupture?

Yes. Although most popliteal cysts do not rupture, it is possible for a cyst to burst and release its fluid into the surrounding tissues of the calf.

When this happens, you may experience sudden pain and swelling extending down the back of your lower leg. The calf may become tight, tender or discoloured.

However, there's an important warning.

A ruptured popliteal cyst can produce symptoms similar to a blood clot in the leg, known as deep vein thrombosis (DVT).

Because DVT can be a serious medical condition, sudden or increasing calf pain and swelling should never automatically be assumed to result from a ruptured cyst.

Seek urgent medical assessment if these symptoms develop. If you also experience chest pain, shortness of breath or collapse, call emergency services immediately. [3]

How Is a Popliteal Cyst Diagnosed?

If you've developed a persistent lump or swelling behind your knee, it's important to have the condition properly assessed.

A healthcare professional will generally begin by discussing your symptoms, medical history and any existing knee problems. They may examine the area behind your knee and assess your range of movement.

In many cases, a physical examination provides sufficient information to suspect a popliteal cyst. However, imaging may be recommended to confirm the diagnosis or investigate the underlying cause.

Ultrasound: An ultrasound can help determine whether the lump is fluid-filled and confirm the presence of a cyst. A specialised venous ultrasound may also be required when a blood clot is suspected.

MRI Scan: An MRI may be recommended when a more detailed examination of the knee joint is required, particularly if a meniscus tear or another internal knee injury is suspected.

X-rays: Although X-rays cannot directly show a popliteal cyst, they may help identify osteoarthritis or other bone-related problems.

Not everyone with a suspected cyst requires all these investigations. The appropriate tests depend on the symptoms and examination findings.

What Are the Treatment Options for a Popliteal Cyst?

If you're experiencing ongoing swelling or discomfort behind your knee, your first priority is understandably to find some relief.

Treatment generally focuses on managing the swelling and associated pain while identifying and addressing any underlying knee condition.

1. Rest and Activity Modification

Temporarily reducing activities that aggravate your knee is often a sensible first step.

You may need to limit longer walks, running, repetitive squatting or other movements that increase pressure and discomfort behind the knee. However, prolonged complete inactivity isn't generally necessary.

Gentle walking and comfortable knee movement may be maintained, provided they don't significantly aggravate your symptoms.

2. Cold Therapy and Elevation

Applying a cold pack wrapped in a towel for approximately 10–20 minutes may help manage discomfort during a painful flare-up.

Elevating your leg while resting may also help reduce associated swelling. However, these measures won't necessarily resolve the underlying problem responsible for producing excess synovial fluid.

3. Physiotherapy and Rehabilitation

Physiotherapy may play an important role in recovery, particularly when muscle weakness, knee instability or another underlying condition contributes to the problem.

During a painful flare-up, strenuous exercises or activities that place excessive pressure on the knee may need to be modified. Gentle movement and appropriately selected exercises can often be maintained.

As symptoms improve, rehabilitation may focus on restoring knee movement, rebuilding strength in the surrounding muscles and supporting a gradual return to normal activities.

4. Medication and Medical Treatments

Pain-relieving or anti-inflammatory medication may help manage discomfort, although these treatments aren't suitable for everyone.

In some cases, a healthcare professional may consider a corticosteroid injection or draining excess fluid to relieve significant swelling. However, draining the fluid doesn't necessarily prevent the cyst from returning, particularly when the underlying knee condition remains untreated.

Surgery is rarely required solely to remove a popliteal cyst. When surgery is considered, it may involve treating an underlying knee problem that continues contributing to the fluid accumulation.

5. Drug-Free, Non-Invasive Popliteal Cyst Relief with OSMO Patch

If you're looking for a drug-free, non-invasive way to help manage the swelling and associated pain from a medically diagnosed popliteal cyst, the OSMO Patch offers a convenient home treatment option.

Simply apply the patch over the affected area before going to bed and let it work while you sleep.

OSMO Patch is designed to help reduce swelling and associated discomfort without the use of drugs or invasive procedures. The OSMO Patch can offer an effective drug-free option alongside appropriate rest and activity modification.

Discover how OSMO Patch may help you manage popliteal cyst swelling and associated pain — so you can get back to enjoying your everyday activities.

>> Learn More About OSMO Patch for Baker's Cyst Relief → 

(OSMO Patch is not suitable for individuals with seafood or shellfish allergies)

How Long Does a Popliteal Cyst Take to Heal?

Recovery times vary depending on the size of the cyst, the severity of your symptoms and whether another knee condition is contributing to the fluid accumulation.

Some cysts gradually become smaller or disappear without requiring invasive treatment. Others may persist for months or return after initially improving.

One important point to understand is that reducing the swelling doesn't always mean the underlying knee problem has been resolved.

If arthritis, a meniscus injury or another condition continues causing excess fluid production, the cyst may return. Addressing the underlying problem and gradually returning to normal activities can help support longer-term improvement.

 

Frequently Asked Questions About Popliteal Cysts

I've Found a Soft Lump Behind My Knee. Could It Be a Popliteal Cyst?

Yes. A soft swelling or lump behind the knee is a common sign of a popliteal cyst.

You may notice that it feels more prominent when standing or straightening your leg.

However, not every lump behind the knee is a cyst. Other conditions, including vascular problems, can cause swelling in the same area. Any new or persistent lump should be examined by a healthcare professional.

Can I Still Walk or Exercise with a Popliteal Cyst?

Gentle walking may be fine if it doesn't significantly aggravate your symptoms.

However, longer distances, running, deep squatting or strenuous exercise may increase discomfort and tightness behind the knee.

Temporarily reducing aggravating activities and gradually returning to exercise as symptoms improve may help.

Can a Popliteal Cyst Go Away on Its Own?

Yes. Some popliteal cysts gradually reduce in size or disappear without requiring invasive treatment.

However, if an underlying knee condition continues producing excess joint fluid, the cyst may persist or return.

Persistent or worsening symptoms should be assessed by a healthcare professional.

What Happens If a Popliteal Cyst Bursts?

If a popliteal cyst ruptures, fluid can leak into the tissues of the calf, causing sudden pain, swelling and tightness.

These symptoms can resemble a blood clot in the leg.

Because it's not possible to reliably distinguish the two conditions based on symptoms alone, sudden calf pain or swelling requires urgent medical assessment.

Why Does My Popliteal Cyst Keep Coming Back?

A popliteal cyst may return when the underlying knee condition continues causing excess synovial fluid to accumulate.

This is particularly relevant when arthritis, cartilage damage or another internal knee problem is present.

Simply reducing or draining the fluid may not prevent recurrence if the underlying cause remains untreated.

Will I Need Surgery to Get Rid of a Popliteal Cyst?

Not necessarily.

Many popliteal cysts improve with conservative treatment, particularly when the underlying cause of the swelling is properly managed.

Surgery is generally reserved for selected cases involving persistent symptoms or an underlying knee problem that requires surgical treatment.

When Should You Seek Medical Attention?

If you've developed a lump or swelling behind your knee, it's sensible to have the condition properly assessed before assuming it's a popliteal cyst.

Seek urgent medical attention if you experience sudden or increasing calf pain, swelling, redness or warmth, particularly when symptoms develop unexpectedly.

These can be signs of a ruptured cyst, but they can also indicate deep vein thrombosis.

If you develop sudden shortness of breath, chest pain or collapse, call 000 in Australia immediately.

Medical References

[1] American Academy of Orthopaedic Surgeons (AAOS): Baker's Cyst (Popliteal Cyst). Read the AAOS medical resource

[2] Healthdirect Australia: Baker's Cysts – Symptoms and Treatment. Read Healthdirect's medical guidance

[3] Mayo Clinic: Baker Cyst – Symptoms and Causes. Read the Mayo Clinic medical resource