Private Knee Ultrasound London: Baker's Cyst, Effusion, Sports Injuries and When You Need a Scan

The knee is the largest and one of the most complex joints in the body. It bears your full body weight, absorbs enormous forces during sport and exercise, and is vulnerable to a wide range of injuries and degenerative conditions. When something goes wrong — swelling, pain, instability, or a visible lump — you want answers.

A private knee ultrasound provides detailed, real-time imaging of the soft tissue structures around your knee: tendons, ligaments, bursa, and joint fluid. It can identify Baker's cysts, effusions, tendon tears, bursitis, and collateral ligament injuries — all in a single appointment with a doctor who explains findings as they appear on screen.

At The Wellness London, every knee ultrasound is performed by a GMC-registered doctor. The key advantage over MRI for many knee conditions is dynamic assessment — your doctor can watch structures move in real time as you bend and extend your knee, identifying problems that a static MRI image may miss.

Knee pain or swelling? Book your scan on WhatsApp or email team@thewellnesslondon.com.

What a Knee Ultrasound Examines

Suprapatellar pouch and joint effusion. The first assessment checks for fluid within the knee joint. Even small effusions (5–10ml) are detectable on ultrasound. Joint effusion indicates inflammation, injury, infection, or arthritis and guides clinical management.

Quadriceps tendon. The tendon connecting the quadriceps muscle to the top of the kneecap. Assessed for tendinopathy, partial tears, and complete rupture. Quadriceps tendon rupture is a surgical emergency — ultrasound provides rapid diagnosis.

Patellar tendon. The tendon from the bottom of the kneecap to the tibial tuberosity. Patellar tendinopathy ("jumper's knee") is common in athletes. Ultrasound shows tendon thickening, hypoechoic areas, and neovascularisation on Doppler.

Collateral ligaments. The medial collateral ligament (MCL) and lateral collateral ligament (LCL) are assessed for thickening, tears, and instability. MCL injuries are particularly common in contact sports.

Baker's cyst (popliteal cyst). A fluid-filled swelling behind the knee, arising from the gastrocnemius-semimembranosus bursa. Baker's cysts are the most common cause of a palpable lump behind the knee. Ultrasound confirms the diagnosis, measures the cyst, assesses for internal debris, and checks for rupture — a ruptured Baker's cyst can mimic DVT with calf swelling and pain.

Bursae. Multiple bursae around the knee can become inflamed. Prepatellar bursitis ("housemaid's knee"), infrapatellar bursitis, and pes anserine bursitis are all clearly visible on ultrasound.

Iliotibial band (ITB). Assessed for thickening and fluid at the lateral femoral condyle — ITB friction syndrome is a common cause of lateral knee pain in runners and cyclists.

Meniscal cysts. Parameniscal cysts (fluid collections adjacent to the meniscus) can be identified on ultrasound and often indicate an underlying meniscal tear.

Dynamic assessment. Your doctor moves the knee through range of motion during the scan, assessing stability, subluxation, and impingement — information that MRI cannot provide.

Baker's Cyst: Everything You Need to Know

Baker's cysts are one of the most common reasons patients book a knee ultrasound. They typically present as a visible or palpable swelling behind the knee that may be painless or cause a feeling of tightness, particularly when bending the knee fully or straightening it completely.

Causes. Baker's cysts almost always occur secondary to an underlying knee condition — osteoarthritis, meniscal tears, rheumatoid arthritis, gout, or other inflammatory conditions cause the knee to produce excess fluid, which herniates posteriorly through a weakness in the joint capsule.

Diagnosis. Ultrasound is the investigation of choice. It confirms the cyst, measures its dimensions, assesses its internal contents (simple fluid vs. debris or septations), and checks for complications.

Complications. A Baker's cyst can rupture, releasing fluid into the calf. This causes sudden calf pain, swelling, and tenderness — symptoms that closely mimic DVT. Ultrasound can differentiate between a ruptured Baker's cyst and DVT, which is critical because the treatments are completely different.

Treatment. Small, asymptomatic Baker's cysts usually require no treatment. Symptomatic cysts may be aspirated under ultrasound guidance. The underlying knee pathology should be addressed to prevent recurrence.

Think you have a Baker's cyst? Book on WhatsApp.

Knee Ultrasound vs. MRI: Which Do You Need?

Choose ultrasound when: Your concern involves tendons, ligaments (MCL/LCL), bursae, effusion, Baker's cyst, or soft tissue structures around the knee. You want dynamic assessment. You want immediate results.

Choose MRI when: Your doctor suspects meniscal tear (internal cartilage), cruciate ligament injury (ACL/PCL), bone pathology, cartilage damage, or intra-articular loose bodies. MRI provides superior assessment of internal joint structures.

Ultrasound first, MRI if needed: Many patients benefit from an ultrasound first — it provides immediate answers for the most common knee conditions and helps determine whether MRI is actually necessary. This approach saves time and avoids unnecessary MRI scans.

Knee Scans at The Wellness London: Pricing

Ultrasound-guided knee procedures:

All prices include the doctor-performed scan, verbal debrief, and same-day written report.

What to Expect During Your Knee Ultrasound

No preparation is needed. Wear shorts or loose trousers that can be rolled above the knee.

You will sit on an examination bed or chair. The doctor applies warm gel and systematically examines the front, sides, and back of the knee. You may be asked to bend and straighten the knee during the scan for dynamic assessment.

The scan takes approximately 20–30 minutes. Your doctor explains findings during the scan and discusses treatment options immediately afterwards. A written report is issued the same day.

Frequently Asked Questions

Is a knee ultrasound painful? No. The probe is moved gently over the skin surface. If your knee is already swollen or tender, you may feel mild discomfort, but the scan itself is non-invasive.

Can ultrasound diagnose arthritis? Ultrasound can identify secondary features of knee arthritis — joint effusion, synovial thickening, osteophytes, and Baker's cyst formation. X-ray remains the standard initial investigation for assessing the degree of joint space narrowing in osteoarthritis, but ultrasound provides complementary information about soft tissue involvement.

Can both knees be scanned? Yes. Bilateral knee assessment is possible in the same appointment and is useful for comparison.

I have a lump behind my knee — is it a Baker's cyst? Most likely, yes. Baker's cyst is by far the most common cause of a popliteal (behind-the-knee) mass. Ultrasound will confirm the diagnosis and rule out other causes such as popliteal artery aneurysm or soft tissue tumour.

Book Your Knee Ultrasound

📱 Book via WhatsApp

📧 Email: team@thewellnesslondon.com

🌐 Book online: thewellnesslondon.com/ultrasound

This article was reviewed by the clinical team at The Wellness London. All scans are performed by GMC-registered doctors. Last updated March 2026.

Medical disclaimer: This information is for educational purposes and does not replace professional medical advice. If your knee is locked, giving way, or you experienced a significant injury, please seek medical assessment promptly.