A soft, swollen lump behind the knee that aches when you bend, walk or run is often a Baker's cyst, also called a popliteal cyst. While the cyst itself is rarely serious, it's almost always a sign that something else is going on inside the knee joint. At Body Advance, we specialise in effective knee pain treatment that eases swelling, restores movement and addresses the underlying cause so the cyst is less likely to return. Our tailored approach combines hands-on therapy, structured rehabilitation and clear, practical advice, helping you return to the activities you love. With expertise in sports massage and pain management, our objective is to support a full recovery and long-term knee health.
Table of Contents
Brief Overview
A Baker's cyst, or popliteal cyst, is a fluid-filled swelling at the back of the knee. According to the NHS, it's most common in adults over 40 and is usually a downstream effect of an underlying knee problem such as osteoarthritis or a meniscus tear. Most cysts respond well to conservative care: rest, structured rehabilitation, hands-on therapy and gradual strengthening of the muscles around the knee. Larger or persistent cysts may benefit from input from your GP. At Body Advance, we focus on the whole movement chain to ease symptoms and reduce the chance of the cyst returning.
Key Highlights
- A Baker's cyst is a fluid-filled swelling behind the knee, almost always linked to an underlying joint problem.
- Osteoarthritis and meniscus tears are the two most common causes in adults.
- Most cysts respond to conservative care; aspiration alone has a recurrence rate above 50% without rehab.
- Hands-on therapy, including manual lymphatic drainage and sports massage, helps shift fluid and reduce knee strain.
- Phased exercises and supportive footwear protect the knee for the long term.
What Is a Baker's Cyst?
A Baker's cyst is a fluid-filled swelling that develops at the back of the knee. It forms when extra synovial fluid (the lubricant inside the joint) is pushed into a small pouch behind the knee, creating a soft, balloon-like bulge.
Anatomically, the cyst sits in a space called the gastrocnemius-semimembranosus bursa, between the calf muscle and a hamstring tendon. There's a tiny one-way valve between this bursa and the knee joint. When the joint produces extra fluid (because of arthritis, a meniscus tear or another problem), the valve allows fluid to escape backward into the bursa but doesn't easily let it return. Over time, the cyst grows.
Doctors describe two types:
- Primary (idiopathic) Baker's cysts: more common in children, with no underlying knee problem. These usually resolve on their own.
- Secondary Baker's cysts: almost always seen in adults, where the cyst is a downstream effect of an underlying knee condition.
Named after the 19th-century surgeon William Morrant Baker, the cyst is most common in adults over 40, according to the NHS, and often resolves once the underlying knee problem is addressed. We see Baker's cysts regularly as part of knee pain treatment in Doncaster, particularly in active adults whose knees take repeated impact through running, cycling or contact sport. If you're a runner, our running massage and recovery guide explains how to keep training while protecting your knees.
How Big Can a Baker's Cyst Get?
Baker's cysts vary widely in size, from a small grape (1 to 2 cm) to a large plum (5 to 7 cm) or, occasionally, even larger. Smaller cysts are often only noticed when bending the knee fully, while larger cysts can be visible when standing and create a noticeable feeling of fullness behind the knee. Size doesn't always correlate with pain. Some small cysts ache constantly, while some larger ones cause no pain at all.
Most cysts are stable in size for long periods, growing slowly as the underlying joint problem progresses. Sudden growth, increasing pain or warmth around the knee should always be checked by a clinician. If you'd like a thorough assessment of your knee and the surrounding joints, we offer acute and chronic pain consultations in Doncaster. Most appointments are available within a few days.
What Causes a Baker's Cyst?
A Baker's cyst is usually a symptom rather than a stand-alone condition. Common triggers include:
- Osteoarthritis of the knee: the most common cause in adults over 50; worn cartilage produces extra fluid as the joint becomes irritated
- Meniscus (cartilage) tears: common in runners, footballers and skiers
- Rheumatoid arthritis and other inflammatory joint diseases
- Gout: uric acid crystals trigger inflammation and excess fluid
- Knee injuries from sport, falls or twisting movements
- Repetitive strain in cyclists, runners and labourers
Identifying the root cause is the key to lasting relief. A cyst that's drained without treating the underlying issue almost always returns, often within weeks. Versus Arthritis notes that managing the joint problem behind the cyst is usually more important than treating the cyst itself.
| Underlying Cause |
Why It Drives a Cyst |
Typical Treatment Focus |
| Osteoarthritis (OA) |
Worn cartilage produces extra synovial fluid |
Strengthening, weight management and hands-on therapy (see NICE OA guidance) |
| Meniscus tear |
Altered joint mechanics irritate the lining |
Targeted rehab; some tears need keyhole surgery |
| Rheumatoid arthritis |
Inflammatory disease increases fluid production |
Specialist medical management plus rehab |
| Gout |
Uric acid crystals trigger inflammation |
GP-led management plus joint care |
| Repetitive strain (running, cycling, manual work) |
Joint can't recover between sessions |
Load management, technique review and hands-on therapy |
This table outlines the most common drivers of Baker's cysts and the treatment focus we apply for each. Lasting relief comes from addressing the cause, not just the cyst.
The Osteoarthritis Link
Osteoarthritis (OA) is responsible for around half of adult Baker's cysts. As cartilage wears, the knee becomes less stable and produces more synovial fluid as a protective response. Over time, this fluid finds its way into the bursa and a cyst develops. Treating the OA itself (through strengthening, weight management and hands-on therapy) usually shrinks the cyst over time.
The Meniscus Tear Link
Meniscus tears are the second most common driver. A tear changes how forces transfer through the knee, irritating the joint lining and producing extra fluid. Some tears settle with conservative care; others may need keyhole surgery. If your knee pain radiates into the calf or thigh, see our page on leg pain treatment in Doncaster. Referred pain is common when surrounding muscles tighten in protection.
Risk Factors and Who Gets Baker's Cysts
Baker's cysts can affect anyone, but some groups are more prone:
- Adults over 40: particularly those with osteoarthritis or previous knee injuries
- Runners and high-impact athletes: especially with sudden mileage increases or worn shoes
- People with rheumatoid arthritis or gout
- Those with previous meniscus or ligament injuries
- Manual workers who kneel, squat or twist regularly
- People carrying excess weight: every kilo above ideal body weight loads the knee 3 to 5 times during walking, more during running
Women are slightly more affected than men, mainly because rheumatoid arthritis and OA are more common in women over 50. Genetics, hormone changes and joint structure all play a role. If your knees feel particularly stiff after sitting for long periods or first thing in the morning, take a look at our knee pain blog for additional self-help tips.
Symptoms of a Baker's Cyst
Some Baker's cysts cause no pain and are only noticed by sight or touch. Others limit movement and ache during activity. Common symptoms include:
- A soft, fluid-filled lump behind the knee
- Tightness or fullness when bending the knee
- Aching or sharp pain that worsens with activity
- Stiffness, especially after rest or first thing in the morning
- Mild swelling extending into the calf
- A clicking, catching or locking sensation if there's an underlying meniscus tear
- Reduced range of motion when fully bending or straightening the knee
Is It Definitely a Baker's Cyst?
Several other conditions can cause a lump behind the knee. The most important to rule out are:
- Lipoma: a benign fatty lump, usually soft and squishy
- Ganglion cyst: typically firmer and smaller than a Baker's cyst
- Popliteal aneurysm: a vascular condition; can pulse if you press on it
- Soft tissue tumour: uncommon but always worth excluding for hard or rapidly growing lumps
If the lump is hard, growing rapidly, painful at night or changing colour, see your GP promptly.
Ruptured Baker's Cyst
If the cyst ruptures, you may notice sudden sharp pain, bruising in the calf and increased swelling. These symptoms can mimic a deep vein thrombosis (DVT). If you're unsure, contact NHS 111 or your GP without delay.
How a Baker's Cyst Is Diagnosed
A clinician can often diagnose a Baker's cyst from a physical examination by feeling the lump, checking knee range of motion and asking about your history. If the diagnosis is unclear, or to investigate the underlying cause, your GP may arrange:
- Ultrasound: quick, painless and excellent for confirming a fluid-filled cyst. It can also rule out a DVT.
- MRI scan: detailed view of cartilage, ligaments and any meniscus damage. Most useful when the cause is unclear or surgery is being considered.
- Knee X-ray: useful if osteoarthritis is suspected, since it shows joint space narrowing and bone changes.
- Blood tests: if rheumatoid arthritis or gout is suspected.
At Body Advance, our therapists carry out a thorough movement assessment, identify likely contributing factors and recommend further imaging via your GP where appropriate. We don't replace medical diagnosis; we work alongside it. You can book a knee assessment online at any time.
What to Expect at Your Body Advance Assessment
Your first session lasts around 60 minutes. We'll discuss your medical history, examine the knee, look at how you stand, walk and squat, and check the surrounding joints. Tight calves, weak glutes and stiff hips often play a role in knee problems.
Here's the typical sequence:
- Conversation: symptoms, work, sport and what makes the knee better or worse.
- Postural and movement assessment: standing posture, gait, single-leg balance, squat.
- Knee examination: range of motion, joint stability, palpation of the cyst.
- Surrounding joint check: hip, ankle and lumbar spine.
- Treatment: typically hands-on therapy plus a guided exercise to take home.
- Plan: clear next steps, expected timeline, any GP referrals needed.
We treat the whole movement chain, not just the painful spot. The Chartered Society of Physiotherapy recommends this kind of whole-body approach to musculoskeletal pain. Our client testimonials share the experiences of people we've treated for similar knee issues, and our about page explains the philosophy behind our approach.
Effective Baker's Cyst Treatment Options
Treatment focuses on two things: easing the cyst itself and addressing the underlying knee problem. Most people respond well to conservative care.
1. Rest, Ice and Compression (RICE)
For acute flare-ups:
- Rest the knee from aggravating activity for a few days
- Ice the back of the knee for 15 minutes, 3 to 4 times a day
- Compression with a soft knee sleeve can ease swelling
- Elevate the leg when sitting
After the first 72 hours, switch to gentle heat before activity and ice afterwards. Heat helps muscles relax before exercise; ice settles any post-activity flare.
2. Settling Symptoms at Home
Beyond the RICE basics, gentle movement throughout the day stops the knee stiffening up. Supportive footwear, avoiding deep squats during a flare-up, and breaking up long periods of sitting all help. The NICE guidance on osteoarthritis is worth a read if your cyst is OA-related, since long-term knee health and cyst recurrence are closely linked. For anything beyond home care, your GP is the right person to speak to.
3. Hands-On Therapy
This is where we make the biggest difference. Targeted sports massage in Doncaster reduces tightness in the calf, hamstrings and quadriceps. These are the muscles that often pull abnormally on the knee when a cyst is present.
We also use manual lymphatic drainage to help shift fluid build-up around the joint. This is particularly effective for Baker's cysts, since the technique works directly with the lymphatic system that processes excess fluid. Deep oscillation therapy settles inflammation and accelerates recovery using gentle electrostatic vibration. For chronic, restricted tissue, myofascial release frees up connective tissue and improves how the knee tracks during movement.
To understand more about how connective tissue affects pain, see our guide to fascia, myofascial release and mobility, or our piece on how fascia and chronic pain are linked for the wider context.
4. Medical Procedures
For large or persistent cysts, GPs sometimes discuss procedures with patients, including aspiration (drawing the fluid out with a fine needle, often guided by ultrasound). These are decisions for your medical team. Whichever route you take, the longer-term picture depends on what's happening inside the joint. Studies suggest aspiration on its own has a recurrence rate above 50%, which is why ongoing rehabilitation and hands-on therapy alongside any medical procedure tend to produce better results.
5. Treating the Underlying Cause
Lasting relief comes from treating the joint problem behind the cyst. That might mean rehabilitation for a meniscus injury, strengthening for arthritis, or a tailored running plan. Our runner's knee and IT band guide is a useful read if your symptoms are training-related, and our muscle strain recovery tips cover nutrition, sleep and load management.
6. When Surgery Is Considered
Surgery is uncommon but may be discussed when conservative treatment hasn't worked, or to address the underlying knee problem (for example, arthroscopic meniscus repair). The British Journal of Sports Medicine highlights that most knee issues respond well to conservative care, so surgery is generally a last resort. Most people improve well before this stage.
Exercises to Support Recovery
Strengthening the muscles around the knee improves stability and reduces the strain that drives cyst formation. Always start gently, and stop if pain rises above 3 out of 10. Build up over weeks, not days.
Phase 1: Pain Settling (Week 1 to 2)
- Heel slides: lying on your back, slowly slide the heel toward your bottom, then straighten. 10 to 15 reps, 2 to 3 times daily.
- Static quad sets: sitting with the leg straight, tighten the thigh and press the back of the knee down. Hold 5 seconds, 10 reps.
- Calf pumps: ankle up and down, 20 reps every hour or so.
Phase 2: Building Strength (Week 2 to 4)
- Straight leg raise: lying on your back with one knee bent, lift the straight leg to the height of the bent knee. Hold 2 seconds. 3 sets of 10.
- Wall sit: back against a wall, slide down to about 45 degrees. Hold 15 to 30 seconds. 3 sets.
- Standing hamstring curl: holding a chair, bend the knee to bring your heel toward your bottom. 3 sets of 10 to 12.
- Calf raises: rise up onto the balls of your feet, hold 1 second, lower slowly. 3 sets of 12 to 15.
Phase 3: Functional Progression (Week 4+)
Knee-Friendly Cross-Training
Maintain fitness without irritating the knee:
- Swimming and aqua jogging: minimal load with full range of motion
- Stationary cycling: keep the saddle high to reduce knee bend
- Pilates and reformer work: excellent for hip and glute strength
- Walking: softer surfaces are usually safer than concrete
Common Mistakes to Avoid
- Ignoring the lump because it doesn't hurt. A pain-free cyst can still flag underlying joint damage worth investigating.
- Stretching aggressively. Forced bending can rupture the cyst.
- Returning to running too soon. Build up gradually with pain-free walking first, then jog-walk intervals over several weeks.
- Skipping the hips and glutes. Weak hip muscles transfer load straight to the knee.
- Trying to drain the lump yourself. Aspiration must be done by a clinician under sterile conditions.
- Sitting still for long periods. Prolonged sitting stiffens the knee and worsens swelling. Stand and move every 30 to 45 minutes.
- Wearing worn-out shoes. Old, compressed shoes change how forces travel through the knee. Replace running shoes every 500 to 800 km.
If knee pain has been hanging around, it's worth getting it checked. Book a knee assessment online. Most appointments are available within a few days.
Returning to Sport After a Baker's Cyst
Once pain settles and strength returns, the priority is rebuilding tolerance gradually:
- Pain-free walking: 30 minutes daily without a flare-up
- Walk-jog intervals: 5 minute walk, 1 minute jog, repeated 5 times
- Easy steady jog: 10 to 20 minutes
- Add intensity: hills, tempo and intervals (one new variable per week)
- Return to full sport: with continued maintenance work
The 10% rule is helpful: increase distance, time or intensity by no more than 10% per week. If pain or swelling returns, drop back a week and rebuild. Cross-train on rest days with cycling or swimming. Many of our long-term clients book monthly maintenance massage to stay ahead of niggles. See the benefits of sports massage for why this matters for ongoing knee health.
Preventing Future Cysts
The best way to prevent a Baker's cyst is to look after the knee:
- Build strength in the quads, hamstrings, glutes and calves
- Maintain a healthy weight: every kilo lost reduces knee load several times over during walking and running
- Vary your training rather than running the same loop daily
- Wear supportive footwear: replace running shoes regularly and avoid worn work boots
- Address niggles early: small aches caught early rarely become big problems
- Strengthen the hips: strong glutes are one of the best knee protectors there is
- Stay mobile: daily knee, hip and ankle mobility takes 5 minutes
- Manage arthritis: if OA is in the picture, regular hands-on therapy and exercise keep the joint moving
When to Seek Professional Help
Speak to a clinician if:
- The lump grows or becomes more painful
- You can't fully bend or straighten the knee
- You notice redness, warmth or fever (possible infection)
- You experience sudden calf swelling or pain (possible rupture or DVT)
- Home treatment hasn't helped after two weeks
- The knee gives way or locks during activity
Browse our full range of pain management treatments at Body Advance to see how we support knee recovery. We don't require a GP referral, so you can book directly.
Get Lasting Relief at Body Advance
A Baker's cyst can be unsettling, but it's very treatable. At Body Advance, we'll work out why your knee is producing extra fluid, ease your symptoms with targeted hands-on therapy, and rebuild the strength and mobility your knee needs to stay healthy. Whether your cyst is new and painful or a long-standing nuisance you've finally decided to tackle, we'll meet you where you are. Most clients see meaningful improvement within a few sessions.
Book a knee assessment online or contact our Doncaster clinic. We'll get you back to moving freely. Read what our patients say on our testimonials page.
