Can a Baker's cyst in the lower leg cause swelling, firmness, and pain?

Baker's Cyst Can Cause Lower Leg Swelling, Firmness, and Pain

Yes, a Baker's cyst can definitively cause swelling, firmness, and pain in the lower leg, particularly when the cyst extends into the calf or ruptures. 1

Clinical Presentation of Baker's Cyst

Baker's cysts are fluid accumulations in the bursa of the gastrocnemius or semimembranosus muscles that communicate with the knee joint space. 1 The characteristic symptoms include:

• Swelling and tenderness behind the knee that may worsen with exercise and can be present at rest 1
• Pain that worsens with knee movement or exercise 1
• Feeling of tightness or fullness behind the knee 1
• Visible and palpable swelling in the popliteal fossa, especially with the knee extended 1
• Fluctuant mass that may increase in size with knee extension 1

Extension Into the Lower Leg

A critical feature is that Baker's cysts can extend far into the thigh and calf muscles, which explains lower leg involvement. 1 This extension can be detected on physical examination and is clearly visualized with imaging. 1, 2

When the cyst extends into the calf, patients experience:

• Swelling in the calf region 3
• Firmness from the fluid-filled mass 4
• Pain that may be severe 3

Ruptured Baker's Cyst: A Critical Complication

Rupture of a Baker's cyst causes sudden calf pain and swelling that can mimic deep vein thrombosis (DVT). 1, 3 This occurs when:

• The cyst ruptures, causing dissemination of fluid into the calf 1
• Patients present with severe pain and swelling in the calf and foot 3
• The clinical presentation is so similar to DVT that ultrasound Doppler is required to differentiate between the two conditions 3

A 2021 case report described a patient who presented with severe pain and swelling in the calf and foot six weeks after initial knee pain, initially suspected to be DVT, but ultimately diagnosed as a ruptured Baker's cyst. 3

Diagnostic Approach

Ultrasound is the preferred initial diagnostic tool to confirm the presence of a Baker's cyst and can accurately diagnose cyst rupture. 1, 2

Key ultrasound findings include:

• Comma-shaped appearance between the medial head of gastrocnemius and semimembranosus tendon 1, 2
• Visualization of extensions into thigh and calf muscles 2
• Differentiation between simple cysts (fluid only) and complex cysts (fluid and solid components) 2

Important Clinical Pitfalls

The most critical pitfall is mistaking a ruptured Baker's cyst for DVT, as both present with calf pain and swelling. 1, 3 Always obtain ultrasound imaging to differentiate these conditions, as management differs significantly. 3

Rare but serious complications include:

• Popliteal artery compression causing lower limb ischemia and intermittent claudication 5
• Hematoma formation within the cyst extending into the calf 4
• Compartment syndrome (rare) 4