Bursitis, Synovial Cyst, and Baker’s Cyst: Knee Cystic Swelling – Diagnosis and Management

1️⃣ KEY DIAGNOSIS COMPARISON TABLE (VERY HIGH-YIELD)

Feature	Bursitis	Synovial Cyst	Baker’s Cyst (Popliteal Cyst)
Definition	Inflammation of a bursa	Herniation of synovial lining	Posterior knee synovial cyst
Origin	Bursa (extra-articular)	Synovium	Synovium
Common location	Prepatellar, infrapatellar, pes anserine	Near joint line	Popliteal fossa
Joint communication	❌ No	✅ Yes	✅ Yes
Compressible	±	✅	✅
Changes with movement	❌ Minimal	±	✅ Size varies with knee movement
Pain with walking	±	±	✅ Common
Common associations	Repetitive trauma, kneeling, infection	OA, RA, chronic synovitis	OA, RA, meniscal tear
Redness / warmth	± (if septic)	❌	❌
Key complication	Septic bursitis	Recurrence	Rupture → pseudo-DVT
First-line imaging	Ultrasound	Ultrasound	Ultrasound
Exam buzzword	“Housemaid’s knee”	Chronic joint disease	Posterior knee swelling

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2️⃣ MANAGEMENT COMPARISON TABLE (OPD-BASED, EXAM-STYLE)

✅ Management Setting All 3 conditions → OPD (unless septic or severe complications)

🩺 A. BURSITIS

Aspect	Management
Definitive treatment	Rest, avoid pressure, NSAIDs
If large/painful	Aspiration (after excluding infection)
If septic	Antibiotics ± drainage
❌ Avoid	Steroid injection if infection suspected
Key principle	Treat inflammation, not surgery first

🩺 B. SYNOVIAL CYST

Aspect	Management
Definitive treatment	Treat underlying joint disease
Symptomatic relief	NSAIDs, activity modification
Aspiration	Temporary benefit (high recurrence)
Surgery	Rare, persistent symptoms only
Key principle	Cyst is a result, not the disease

🩺 C. BAKER’S CYST (MOST TESTED)

Aspect	Management
Definitive treatment	Treat intra-articular pathology
Mild symptoms	Observation + NSAIDs
Moderate symptoms	Aspiration + steroid injection
Persistent/recurrent	Arthroscopic knee treatment
❌ Avoid	Isolated cyst excision early
Key principle	Never treat cyst alone

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3️⃣ FOLLOW-UP CHEAT SHEET (EXAM-READY)

⏱ WHEN TO FOLLOW UP?

Condition	Follow-up timing	What to assess
Bursitis	1–2 weeks	Pain, swelling, signs of infection
Synovial cyst	4–6 weeks	Size, symptoms, joint disease control
Baker’s cyst	2–4 weeks	Walking pain, recurrence, ROM

🚨 RED FLAGS → EARLY RETURN / REFERRAL

Red Flag	Why important
Fever, redness, warmth	Suspect septic bursitis
Rapid calf swelling & pain	Rule out DVT vs ruptured Baker’s cyst
Neurovascular symptoms	Compression complication
Persistent pain >6 weeks	Consider MRI / ortho referral

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4️⃣ ONE-LOOK EXAM MEMORY BOX 🧠

Posterior knee + compressible + worse with walking → Baker’s cyst

Anterior knee + kneeling history → Bursitis

Recurrent cyst + OA/RA → Synovial cyst

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5️⃣ OSCE ONE-LINE ANSWERS (STEAL THIS)

• Diagnosis: “Most consistent with Baker’s cyst secondary to knee osteoarthritis”

• Investigation: “Ultrasound of knee and popliteal fossa”

• Management: “Treat underlying knee pathology, NSAIDs, observation”

• Follow-up: “Review in 2–4 weeks or earlier if worsening”

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6️⃣ COMMON EXAM TRAPS

❌ Treating Baker’s cyst surgically first ❌ Forgetting DVT mimic ❌ Calling bursitis a joint disease ❌ Missing underlying OA or meniscal tear

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“A patient presents with a soft mass around the knee, compressible, reduces on pressure, and painful on walking.”

Cystic and Bursal Lesions Around the Knee

Bursitis, Synovial Cyst, and Baker’s Cyst: Diagnosis and Management

1. BURSITIS

Definition

Bursitis is inflammation of a bursa, a fluid-filled sac that reduces friction between bone, tendon, and skin.Around the knee, common bursae include:

• Prepatellar bursa

• Infrapatellar bursa

• Pes anserine bursa
  

Pathophysiology

• Repetitive friction, trauma, pressure, or infection → inflammation of bursa

• Increased synovial fluid → localized swelling

• Can be aseptic or septic
  

Clinical Features

• Localized swelling over bursa

• Soft or fluctuant mass

• Tenderness

• Pain worsened by movement or pressure

• Skin may be warm or erythematous (especially in septic bursitis)

• Usually does NOT communicate with knee joint
  

Diagnosis

• Clinical diagnosis is usually sufficient

• Ultrasound: fluid-filled sac outside joint

• Aspiration (if infection suspected):

  • Cell count

  • Gram stain & culture

  • Crystal analysis
    

Management

A. Non-Septic Bursitis (Most common)

Definitive Treatment

• Activity modification

• Avoid kneeling or repetitive pressure

• NSAIDs (e.g., ibuprofen)

• Consider aspiration if large or painful

• Corticosteroid injection (only after infection excluded)

Supportive Treatment

• Rest

• Ice

• Compression

• Elevation
  

B. Septic Bursitis

Definitive Treatment

• Aspiration and drainage

• Antibiotics (cover Staphylococcus aureus)

Supportive Treatment

• Immobilization

• Analgesia

• Monitor systemic signs

Exam Pearl

✅ Pain + localized swelling over bony prominence ❌ Usually no connection to joint capsule

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2. SYNOVIAL CYST

Definition

A synovial cyst is a fluid-filled sac arising from the synovial lining of a joint or tendon sheath, caused by increased intra-articular pressure.

Pathophysiology

• Chronic joint disease → increased synovial fluid

• Herniation of synovium through capsule

• Fluid-filled cyst remains connected to synovium
  

Clinical Features

• Soft, fluctuant mass near joint

• Compressible

• May fluctuate in size

• Often painless, but can cause discomfort with movement

• Associated with:

  • Osteoarthritis

  • Rheumatoid arthritis

  • Meniscal tears
    

Diagnosis

• Ultrasound: cystic lesion with synovial connection

• MRI (if diagnosis unclear or surgical planning)

• Joint evaluation for underlying pathology
  

Management

Definitive Treatment

• Treat underlying joint disease (OA, RA)

• Aspiration (high recurrence)

• Surgical excision if persistent or symptomatic

Supportive Treatment

• Observation if asymptomatic

• NSAIDs for pain
  

Exam Pearl

✅ Associated with chronic joint disease ❌ High recurrence after aspiration alone

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3. BAKER’S CYST (POPILITEAL CYST)

Definition

A Baker’s cyst is a specific type of synovial cyst arising from the posterior knee, usually between:

• Semimembranosus tendon

• Medial head of gastrocnemius
  

Pathophysiology

• Knee joint effusion → increased intra-articular pressure

• One-way valve mechanism allows fluid to collect posteriorly

• Strongly associated with intra-articular pathology
  

Common Associations

• Osteoarthritis

• Rheumatoid arthritis

• Meniscal tear

• Inflammatory arthritis
  

Clinical Features

• Swelling in the popliteal fossa

• Soft, fluctuant, compressible mass

• Size may change with knee movement

• Pain or tightness when walking or extending knee

• May rupture → calf pain mimicking DVT (pseudothrombophlebitis)
  

Diagnosis

• Ultrasound (first-line)

• MRI if underlying knee pathology suspected

• Doppler US if DVT is a concern
  

Management

A. Asymptomatic or Mild

Definitive Treatment

• Treat underlying knee disease

• Observation

Supportive Treatment

• NSAIDs

• Activity modification
  

B. Symptomatic Baker’s Cyst

Definitive Treatment

• Aspiration + corticosteroid injection (temporary relief)

• Arthroscopic treatment of intra-articular cause

• Surgical excision (rare, last resort)

Supportive Treatment

• Rest

• Compression

• Physiotherapy
  

Exam Pearl

✅ Posterior knee swelling ✅ Associated with knee pathology ❌ Treating cyst alone → recurrence

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COMPARISON SUMMARY TABLE

Feature	Bursitis	Synovial Cyst	Baker’s Cyst
Origin	Bursa	Synovium	Synovium
Location	Over bony prominence	Near joint	Popliteal fossa
Joint communication	❌ No	✅ Yes	✅ Yes
Compressible	Sometimes	Yes	Yes
Common association	Trauma, pressure	OA, RA	OA, meniscal tear
Key management	Rest, NSAIDs	Treat joint disease	Treat knee pathology

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Key Take-Home Messages (High-Yield)

• Baker’s cyst = synovial cyst of the knee

• Always treat the underlying joint pathology

• Posterior knee swelling + walking pain → think Baker’s cyst

• Ruptured Baker’s cyst can mimic DVT

• Aspiration alone has high recurrence