Category

Specific Factor

Evidence / Association

Pathophysiologic Rationale

Strong, Consistent Patient Factors

Prior VTE

25‑fold ↑ risk [37]

Persistent hypercoagulability; always triggers pharmacological prophylaxis.

Factor V Leiden / thrombophilia

20–24× ↑ risk [2,15]

Inherited pro‑thrombotic state → activates coagulation cascade.

Active / recent cancer

Up to 12.5 % DVT despite prophylaxis [16]

Tumour tissue factor, chemo‑induced endothelial injury & hypercoagulability.

Diabetes mellitus

OR ≈ 15 [30]; confirmed in newer cohorts

Endothelial dysfunction, ↑ tissue factor, poor wound healing → stasis.

Chronic immobilisation (cast ≥ 2‑8 wk, NWB)

9× ↑ risk for 2-8 week immobilisation [25]; absolute DVT ≈ 2 % [64]

Venous stasis from loss of calf‑pump action.

Moderate‑Strength Patient Factors

Advanced age (≥ 65 y)

Mean age difference ≈ 15 y [9]

Venous stasis, comorbidity burden, longer hospital stay.

Cardiovascular disease (HTN, CAD)

Meta‑analyses show ↑ risk; HF data mixed

Systemic inflammation, ↑ fibrinogen/D‑dimer, endothelial dysfunction.

Elevated BMI (≥ 30 kg m²)

Large cohort (22 500 pts) → major risk; smaller studies inconsistent

↑ Intra‑abdominal pressure → stasis; low‑grade inflammation.

COPD

Significant ↑ VTE below‑knee ortho surgery [19]

Systemic inflammation, longer LOS, hypoxia‑induced coagulopathy.

Female sex (context‑dependent)

Modest ↑ risk in some databases; others neutral

Estrogen exposure, varicose veins, peri‑partum status.

Hormonal therapy (OCP/HRT)

4× ↑ risk within 3 mo [15]

Estrogen ↑ pro‑coagulant proteins & PAI‑1, ↓ protein S.

Surgical / Peri‑operative Factors

Hind‑ / ankle / tibial procedures vs forefoot

OR 1.7–2.5; highest incidence mid‑/hindfoot [3]

More tissue dissection, longer immobilisation.

Achilles tendon rupture

Symptomatic VTE 6.5× higher [52]

Local inflammation adjacent to deep veins.

Prolonged operative time (> 120 min)

Linear ↑ [74]; FA data mixed

Extended stasis, inflammatory activation.

General anaesthesia (vs regional)

OR ≈ 2-3 in some FA cohorts; data mixed

↓ Cardiac output, venous dilatation, platelet activation.

Non‑weight‑bearing first postoperative week

4.3× ↑ DVT if unable to bear < 50 % body-weight on injured limb [67]

Inadequate calf‑pump activation.

Open fractures / complex distal tibia fixation

Higher PE risk OR 1.6; VTE 3.3% [10]

Greater soft‑tissue injury & surgical duration.