Is there an increased risk of developing a thrombus on the lower leg receiving a knee injection in a patient with an Inferior Vena Cava (IVC) filter, without an active Deep Vein Thrombosis (DVT), and not taking anticoagulation?

Risk of Thrombosis with Knee Injection in a Patient with IVC Filter and No Active DVT

There is an increased risk of developing a thrombus in the lower leg receiving a knee injection in a patient with an IVC filter who is not on anticoagulation, even without an active DVT. This risk is supported by evidence showing that IVC filters themselves can promote thrombus formation.

Mechanism of Increased Risk

IVC filters are associated with several thrombotic complications:

• IVC filters can promote thrombus formation as they are intravascular foreign bodies 1
• Long-term adverse effects such as thrombosis of the IVC or lower extremity veins occur in 4% to 32% of patients with IVC filters 1
• Filters reduce the risk of pulmonary embolism but increase the risk of lower extremity DVT 1
• In a case series of patients with heparin-induced thrombocytopenia (HIT) who received IVC filters, 9 out of 10 patients developed new thromboembolic events 1

Knee Injection Considerations

The knee injection procedure introduces additional risk factors:

• Local tissue trauma from the needle can activate the coagulation cascade
• Temporary immobility following the injection may contribute to venous stasis
• The inflammatory response to the injection may promote a prothrombotic state

Anticoagulation Status

The absence of anticoagulation significantly impacts risk:

• IVC filters are primarily indicated for patients who cannot receive anticoagulation 2
• Without anticoagulation, the protective effect against thrombus formation is absent
• Research shows that patients with IVC filters who are not on anticoagulation have equivalent rates of thrombotic events compared to those on anticoagulation 3

Risk Mitigation Strategies

To reduce thrombotic risk during knee injection:

1. Consider temporary anticoagulation if not absolutely contraindicated
2. Minimize injection trauma by using proper technique and smallest appropriate needle
3. Encourage early mobilization after the procedure
4. Monitor for signs of DVT following the procedure
5. Consider mechanical prophylaxis such as compression stockings

Special Considerations

• If the IVC filter was placed due to a temporary contraindication to anticoagulation, reassess whether anticoagulation can now be safely initiated 2
• The American Society of Hematology recommends against routine insertion of IVC filters and suggests they should be restricted to patients who cannot receive anticoagulation 1, 2
• If a retrievable filter is in place, consider filter removal as soon as anticoagulation can be safely initiated 2

Conclusion

When performing a knee injection in a patient with an IVC filter who is not on anticoagulation, clinicians should be aware of the increased thrombotic risk and implement appropriate preventive measures. The combination of the filter (which itself increases DVT risk) and the local inflammatory response from the injection creates a higher-risk scenario that warrants careful consideration and monitoring.