What causes persistent ankle swelling that worsens at night and how should it be managed?

Ankle Swelling for 2 Months Worsening at Night

For persistent ankle swelling lasting 2 months that worsens at night, you must first rule out venous insufficiency and post-thrombotic syndrome, then systematically evaluate for chronic ankle pathology including ligamentous injury, osteochondral lesions, and tendon abnormalities through clinical examination and MRI if symptoms persist.

Initial Clinical Assessment

The pattern of swelling worsening at night (presumably meaning end of day) strongly suggests venous insufficiency or post-thrombotic syndrome rather than typical ankle sprain sequelae. You need to immediately assess for:

• History of prior deep venous thrombosis (DVT) - symptoms that worsen by end of day or with prolonged standing/walking and improve with rest or limb elevation are characteristic of post-thrombotic syndrome 1
• Pedal pulse examination - absent pulses require vascular evaluation with ankle-brachial index 1
• Skin changes - hyperpigmentation, lipodermatosclerosis, or venous ectasia indicate chronic venous insufficiency 1
• Pain characteristics - heaviness, fatigue, cramping (often at night), itching suggest venous etiology rather than mechanical ankle pathology 1

Diagnostic Pathway

If Venous Insufficiency is Suspected

• Ankle-brachial pressure index should be measured if pedal pulses are diminished or absent 1
• An ankle-brachial index <0.9 indicates peripheral arterial disease, though this may be falsely elevated due to arterial calcification 1
• Consider toe pressure or transcutaneous oxygen pressure (TcPO2) as more reliable alternatives 1

If Mechanical Ankle Pathology is Suspected

Start with plain radiographs (anteroposterior, lateral, and mortise views) to evaluate for osteoarthritis, osteochondral abnormalities, or evidence of prior trauma 1

If radiographs are normal but symptoms persist beyond 6 weeks:

• MRI without IV contrast is the definitive next study - it globally evaluates all anatomic structures including ligaments, tendons, cartilage, and bone 1, 2
• MRI is highly accurate for ligament, tendon, and osteochondral abnormalities and can identify synovitis and impingement lesions 1

Common Pitfalls

Do not assume this is simply a chronic ankle sprain. Residual symptoms 6-18 months after ankle sprain are common (72.6% report residual symptoms), but the pattern of worsening at night is atypical for mechanical ankle pathology 3. Mechanical ankle problems typically worsen with activity and improve with rest, whereas venous insufficiency worsens throughout the day with dependency 1.

Chronic ankle pain after sprains typically presents with:

• Vague diffuse pain localized to lateral/anterolateral ankle 4
• Giving-way sensation, swelling, stiffness, locking and crepitation 4
• Symptoms that worsen with activity, not specifically at night 4

Management Based on Etiology

If Post-Thrombotic Syndrome/Venous Insufficiency

• Compression therapy is the mainstay of treatment 1
• Limb elevation when resting 1
• Avoid prolonged standing or sitting 1

If Chronic Ankle Instability or Ligamentous Injury

• Supervised exercise-based programs are preferred over passive modalities as they stimulate recovery of functional joint stability 1
• Ankle braces (semi-rigid or lace-up) should be used in conjunction with supervised exercise therapy 1, 2
• Surgery should be reserved for cases that do not respond to thorough and comprehensive exercise-based treatment 1

If Intra-articular Pathology Found on MRI

• Osteochondral lesions, meniscoid lesions, or impingement syndromes may require arthroscopic evaluation if conservative treatment fails for at least 6 months 5
• Arthroscopy offers significant improvements for syndesmotic instability and anterior/anterolateral impingement 5

Red Flags Requiring Urgent Evaluation

• Ankle-brachial index <0.6, toe pressure <30 mmHg, or TcPO2 <25 mmHg - these indicate critical ischemia requiring urgent vascular imaging and possible revascularization 1
• Signs of infection - fever, erythema, warmth require urgent evaluation for septic arthritis or soft tissue infection 1
• Diabetes with neuropathy - requires different evaluation approach and heightened concern for ulceration 1, 2