Baker’s Cyst: Symptoms, Treatment, Exercises and Red Flags

A Baker’s cyst is a fluid-filled lump behind the knee. It may cause tightness, aching, stiffness or difficulty bending the knee, although some cysts cause no symptoms. In adults, it often develops because another knee problem produces extra joint fluid. Physiotherapy may help movement, strength and function when the underlying condition is suitable for rehabilitation, but every new or unexplained lump should be checked by a GP. Sudden calf swelling also needs urgent assessment because a ruptured cyst can look similar to a blood clot.

What is a Baker’s cyst?

A Baker’s cyst, also called a popliteal cyst, forms when joint fluid pushes into a small sac at the back of the knee. The size can vary. A small cyst may be found incidentally, while a larger one can create a visible or palpable swelling.

The lump may feel firmer when the knee is straight and softer when it bends. It is usually located in the crease behind the knee rather than within the calf itself. You should not assume that a lump is a Baker’s cyst from appearance alone; a GP may need to rule out other causes.

Baker’s cyst symptoms

The NHS lists a soft lump behind the knee as the main sign. Other possible symptoms include:

• aching or pain behind the knee;
• a feeling of fullness, pressure or tightness;
• knee stiffness or difficulty bending the joint fully;
• clicking or other symptoms from the underlying knee problem;
• leg discomfort or swelling;
• symptoms that become more noticeable after walking or standing.

The cyst itself may not be the main source of pain. Osteoarthritis, inflammatory arthritis or an internal knee injury can produce both the extra fluid and the symptoms that limit activity.

What causes a Baker’s cyst?

In adults, a Baker’s cyst commonly develops when a knee condition increases joint-fluid production. Recognised causes include:

• knee osteoarthritis;
• rheumatoid arthritis or another inflammatory joint condition;
• a meniscus or other knee injury;
• gout;
• previous trauma or irritation inside the joint.

Sometimes no clear cause is found. Baker’s cysts are more common between the ages of 35 and 70, but they can occur at other ages. In children, they are less often linked to joint damage and may settle without treatment.

How is a Baker’s cyst diagnosed?

A GP will ask how the lump and knee symptoms developed and examine the leg. They may check knee movement, swelling and signs of an underlying joint problem. The history also helps identify whether urgent investigation for a blood clot or another condition is needed.

An ultrasound can show whether the lump contains fluid and can help distinguish a cyst from other causes. MRI may be used when more detail about the knee joint or an internal injury is needed. Imaging is not automatically required for every uncomplicated cyst, but it is useful when the diagnosis is uncertain or symptoms suggest another problem.

Do not try to diagnose or drain a lump yourself. Needling a swelling without confirming what it is can cause injury or infection and may miss a more serious diagnosis.

Does a Baker’s cyst go away?

Some Baker’s cysts improve without specific treatment, particularly when they cause few symptoms. Treating the underlying knee problem can also reduce the fluid and pressure that maintain the cyst.

Recovery varies widely. The NHS notes that a Baker’s cyst can take from a few months to a few years to get better. Size does not always match symptoms, and the cyst may fluctuate as the knee becomes more or less irritated. A fixed promise that it will disappear after a certain number of physiotherapy sessions would not be realistic.

A ruptured cyst can cause more sudden calf pain and swelling. Once a blood clot has been ruled out, the leaked fluid is usually reabsorbed over the following weeks, although symptoms can be uncomfortable during that period.

Baker’s cyst treatment

Treatment depends on pain, function and the cause. A cyst that is not troublesome may only need observation and management of the knee condition. Options discussed by NHS services include pain relief, physiotherapy, a corticosteroid injection into the knee, drainage and, less commonly, surgery to repair damage within the joint.

Relative rest during a painful flare

Temporarily reduce activities that markedly increase pressure or swelling, such as long walks, repeated deep squats or prolonged kneeling. This is different from avoiding movement completely. Cambridge University Hospitals advises keeping as mobile as possible, while the NHS suggests resting the knee when symptoms are sore. A practical approach is short periods of comfortable movement with a temporary reduction in aggravating load.

Ice and elevation

The NHS suggests applying an ice pack wrapped in a tea towel for around 10 minutes at a time and raising the leg on a pillow. Do not place ice directly on the skin. Check the skin regularly, particularly if sensation or circulation is reduced.

Pain relief

The NHS lists ibuprofen or paracetamol as options for symptom relief. These medicines are not suitable for everyone. Ask a pharmacist or GP if you have another health condition, take other medicines, are pregnant or are unsure which option is safe.

Injection, drainage or surgery

A clinician may consider an injection into the knee when inflammation from the underlying joint condition is contributing to symptoms. Fluid can sometimes be drained, but a cyst may refill if the knee continues producing excess fluid. Surgery to remove the cyst is uncommon; when surgery is needed, it may focus on the joint damage maintaining it.

Can physiotherapy help a Baker’s cyst?

Physiotherapy does not manually squeeze fluid out of a cyst. Its role is to assess movement and function, identify modifiable aggravating factors and rehabilitate an appropriate underlying knee problem. Treatment may include:

• advice on walking, work, stairs, kneeling and exercise load;
• comfortable knee movement to limit avoidable stiffness;
• progressive thigh, hip and calf strengthening;
• balance and functional exercises;
• a graded return to walking, running, gym training or sport;
• support with an osteoarthritis or post-injury exercise plan;
• referral for medical assessment when the lump, swelling or symptom pattern is unclear.

If osteoarthritis is contributing, NICE recommends therapeutic exercise tailored to the person, including local strengthening and general aerobic fitness. Pain may rise slightly when a new programme begins, but consistent exercise can improve pain and function over time. Manual therapy should only be considered alongside exercise rather than as a stand-alone treatment for knee osteoarthritis.

Baker’s cyst exercises: what is a sensible starting point?

There is no special exercise that reliably makes the cyst disappear. Exercise should target the knee problem and the activities you need to regain. During an irritable phase, examples that a clinician might adapt include:

• Comfortable knee bending and straightening: move through the range available without forcing pressure behind the knee.
• Quadriceps activation: tighten the thigh with the leg supported, then relax.
• Sit-to-stand practice: use a suitable chair height and a controlled range.
• Hip and calf strengthening: build support around the whole lower limb when tolerated.
• Low-impact aerobic activity: short walks or cycling may suit some people, provided the cyst and underlying knee condition tolerate them.

Avoid forcing deep knee flexion when it creates a strong sense of pressure behind the joint. Stop and seek advice if exercise causes rapidly increasing swelling, marked calf pain, heat, redness or breathlessness. Progress should be based on the response over the following day as well as how the movement feels at the time.

When a Baker’s cyst may have ruptured

A cyst can occasionally burst and release fluid into the calf. This may cause sudden pain and swelling behind the knee and lower leg, bruising, warmth or skin colour change. These symptoms can closely resemble deep-vein thrombosis.

Do not rely on home tests to tell the difference. The NHS advises an urgent GP appointment or NHS 111 assessment when leg pain or swelling suddenly worsens, the leg becomes warm or bruised, the skin turns red or darker, or the swelling changes in firmness. An ultrasound may be needed to exclude a blood clot.

Baker’s cyst red flags: when to get urgent help

See a GP for any new lump that has not been diagnosed, even if it is painless.

Contact NHS 111 urgently for sudden or worsening one-sided calf pain and swelling, warmth, bruising, red or darkened skin, or a marked change in the swelling. These can be caused by a ruptured cyst or DVT, and the distinction needs clinical assessment.

Call 999 or go to A&E if leg pain or swelling occurs with chest pain or breathlessness. These may be signs of a pulmonary embolism and require immediate care.

Seek prompt medical assessment if the knee is hot, red and very painful, you feel feverish or unwell, you cannot put weight through the leg after an injury, the knee has changed shape, or the foot becomes cold, pale, blue or numb.

How online physiotherapy may help

A video consultation can explore the history, review visible swelling and movement, discuss activity changes and guide suitable rehabilitation once serious causes have been excluded. Online physiotherapy cannot palpate the lump, perform an ultrasound, drain a cyst or rule out DVT. A new lump or acute calf swelling should be medically assessed before relying on remote exercise advice.

If osteoarthritis is the likely cause, read our guide to knee osteoarthritis exercises and treatment. If symptoms followed twisting, locking or a sports injury, our article on meniscus tear symptoms and recovery may also help you prepare for an assessment.

Frequently asked questions

Should I massage a Baker’s cyst?

Do not apply forceful pressure directly to an unexplained lump. Massage cannot treat every underlying cause and is unsafe when sudden calf swelling has not been assessed. A clinician should first confirm the diagnosis.

Can I exercise with a Baker’s cyst?

Many people can continue or gradually resume exercise, but the type and dose should match the underlying knee condition and symptom response. Reduce activities that sharply increase swelling or pressure, then build strength and aerobic activity progressively.

Will draining the cyst cure it?

Drainage can reduce the fluid, but the cyst may refill if the knee continues producing excess joint fluid. Treatment decisions should address the reason the cyst formed as well as the swelling itself.

Sources

• NHS: Baker’s cyst (accessed 10 November 2026).
• NHS: Deep-vein thrombosis (accessed 10 November 2026).
• NICE NG226: Osteoarthritis in over 16s — diagnosis and management (accessed 10 November 2026).
• Cambridge University Hospitals NHS Foundation Trust: Popliteal cyst information (approved 24 April 2026; accessed 10 November 2026).
• Oxford University Hospitals NHS Foundation Trust: Baker’s cyst (accessed 10 November 2026).

Last reviewed: 10 November 2026. This article provides general information and does not replace an individual medical assessment. Stock photographs are commercially licensed images already hosted by YourPhysio.