Painful swollen leg

A swollen or painful leg is a common clinical presentation in medical and surgical practice. It may be due to benign, chronic conditions (e.g. venous insufficiency) or life-threatening emergencies such as DVT or necrotising fasciitis. A structured approach with early identification of red flags is essential to avoid missed diagnoses.

🧬 Basic Physiology

• Fluid balance in the leg depends on the interplay between:
  • 🫀 Hydrostatic pressure (driving fluid out of capillaries).
  • 🧂 Oncotic pressure (albumin pulling fluid back into circulation).
  • 🦵 Lymphatic drainage (returning excess interstitial fluid).
  • 🚶 Muscle pump + venous valves (preventing venous pooling).
• Disruption in any of these → oedema, swelling, or pain.

⚡ Differential Diagnosis of a Swollen / Painful Leg

• Deep Vein Thrombosis (DVT)
  • 📋 Unilateral swelling, pain, erythema, warmth. 🚨 Risk of pulmonary embolism.
  • 🔎 Doppler ultrasound (first-line), D-dimer, venography (gold standard).
  • 💊 LMWH/DOAC anticoagulation; thrombolysis if massive; compression stockings.
• Cellulitis
  • 📋 Red, hot, tender skin ± fever. Usually unilateral.
  • 🔎 Clinical diagnosis; blood cultures if septic.
  • 💊 Oral/IV antibiotics (flucloxacillin, clindamycin); analgesia, elevation.
• Peripheral Arterial Disease (PAD)
  • 📋 Claudication, cold pale limb, absent pulses, pain worse on elevation.
  • 🔎 ABI <0.9, Duplex Doppler, angiography.
  • 💊 Lifestyle modification, antiplatelets, statins; revascularisation if severe.
• Chronic Venous Insufficiency
  • 📋 Dependent oedema, heaviness, varicose veins, stasis dermatitis.
  • 🔎 Duplex ultrasound for venous reflux.
  • 💊 Compression stockings, leg elevation, endovenous ablation if severe.
• Lymphedema
  • 📋 Non-pitting swelling (late), peau d’orange skin. Often painless.
  • 🔎 Clinical ± lymphoscintigraphy.
  • 💊 Compression therapy, manual lymph drainage, exercise, meticulous skin care.
• Baker’s Cyst
  • 📋 Posterior knee swelling; rupture mimics DVT.
  • 🔎 Ultrasound or MRI.
  • 💊 Aspiration, corticosteroid injection, physiotherapy; surgery if recurrent.
• Trauma (Fractures, Tears)
  • 📋 Local swelling, bruising, reduced ROM, injury history.
  • 🔎 X-ray (bone), MRI/CT (soft tissue).
  • 💊 RICE, immobilisation, surgery if severe.
• Gout
  • 📋 Acute severe pain, swelling, erythema (often 1st MTP, but ankle/knee possible).
  • 🔎 Joint aspiration (urate crystals).
  • 💊 NSAIDs, colchicine, steroids; long-term allopurinol/febuxostat.
• Septic Arthritis
  • 📋 Hot, swollen, exquisitely tender joint + fever.
  • 🔎 Urgent aspiration (Gram stain, culture); blood cultures.
  • 💊 IV antibiotics + joint drainage; orthopaedic input.
• Necrotising Fasciitis
  • 📋 Rapidly spreading pain/swelling, pain “out of proportion”, blistering, systemic toxicity.
  • 🔎 Clinical – do not delay. CT/MRI may show fascial gas.
  • 💊 Emergency surgical debridement, IV broad-spectrum antibiotics, ICU support.

🔎 Key Investigations

• 🧪 Bloods: FBC, CRP, U&E, LFTs, clotting profile.
• 🩺 Imaging: Duplex Doppler US (DVT/venous insufficiency), X-ray/MRI (trauma), lymphoscintigraphy (lymphoedema).
• 💉 Special tests: Joint aspiration (septic arthritis, gout), ABI (arterial disease), blood cultures if infection suspected.

🛠️ General Management Principles

• 🚨 Identify emergencies early: DVT/PE, necrotising fasciitis, septic arthritis → urgent action.
• 🛏️ Supportive care: Rest, elevation, analgesia, treat underlying comorbidities.
• 🧦 Compression: Venous and lymphatic causes respond to stockings/bandaging.
• 💊 Targeted therapy: Anticoagulants for DVT, antibiotics for cellulitis/sepsis, urate-lowering for gout, immunosuppression if vasculitic cause suspected.
• 👩‍⚕️ Multidisciplinary input: Vascular, orthopaedics, rheumatology, dermatology as indicated.

🧑‍⚕️ Clinical Pearls

• Unilateral = think local cause (DVT, cellulitis, trauma).
• Bilateral = think systemic (heart, kidney, liver, venous/lymphatic insufficiency).
• Always assess for pulmonary embolism risk in DVT presentations.
• Pain “out of proportion” = red flag for necrotising fasciitis.

🧾 Clinical Case Examples

Case 1 – Deep Vein Thrombosis (DVT) 🩸 A 62-year-old man develops a swollen, painful left calf after a long-haul flight. On exam: unilateral calf swelling, warmth, and erythema. Wells score = 3. 👉 Likely diagnosis: DVT. 👉 Management: Urgent Doppler US; start DOAC anticoagulation if confirmed.

Case 2 – Cellulitis 🦠 A 70-year-old woman presents with an acutely painful, red, hot, swollen lower leg with fever and rigors. 👉 Likely diagnosis: Cellulitis. 👉 Management: Blood cultures, IV flucloxacillin, elevation, analgesia. Rule out necrotising fasciitis if rapid progression.

Case 3 – Peripheral Arterial Disease (PAD) 🚶 A 55-year-old smoker complains of calf pain after walking 200 m, relieved by rest. Exam: pale, cool foot with absent dorsalis pedis pulse. 👉 Likely diagnosis: PAD / intermittent claudication. 👉 Management: ABI, vascular referral, smoking cessation, statin, antiplatelet.

Case 4 – Chronic Venous Insufficiency 🦵 A 68-year-old man with varicose veins has bilateral ankle swelling, worse in the evenings. He has brown skin discolouration and a healed venous ulcer. 👉 Likely diagnosis: Chronic venous insufficiency. 👉 Management: Duplex US, compression stockings, lifestyle modification, possible endovenous ablation.

Case 5 – Lymphoedema 🌊 A 50-year-old woman develops progressive, non-pitting swelling of her left leg following hysterectomy and pelvic radiotherapy for cervical cancer. 👉 Likely diagnosis: Secondary lymphoedema. 👉 Management: Compression therapy, manual lymph drainage, skin care.

Case 6 – Baker’s Cyst 🥚 A 60-year-old man with osteoarthritis notices a lump behind his knee. It suddenly bursts, causing calf pain and swelling. US excludes DVT. 👉 Likely diagnosis: Ruptured Baker’s cyst. 👉 Management: Symptomatic - analgesia, rest, compression; treat underlying joint disease.

Case 7 – Gout ⚡ A 45-year-old man presents with acute, severe pain and swelling in the ankle joint. The skin is red, shiny, and tender. Past history of hyperuricaemia. 👉 Likely diagnosis: Acute gout. 👉 Management: NSAIDs or colchicine; joint aspiration if diagnosis uncertain. Long-term allopurinol after flare settles.

Case 8 – Septic Arthritis 🚨 A 35-year-old man presents with sudden onset knee pain, swelling, and fever. He is unable to bear weight. 👉 Likely diagnosis: Septic arthritis. 👉 Management: Urgent joint aspiration for Gram stain/culture, IV antibiotics, orthopaedic referral for washout.

Case 9 – Necrotising Fasciitis ⚡ A 58-year-old diabetic man presents with rapidly worsening thigh pain, swelling, and blistering. Pain is out of proportion to findings, BP 80/50, HR 130. 👉 Likely diagnosis: Necrotising fasciitis. 👉 Management: Emergency surgical debridement, IV broad-spectrum antibiotics, ICU support.