Septic Ankle With Purulence Tracking Up the Flexor Hallucis Longus Tendon Sheath Leading to Deep Venous Thrombosis/Pulmonary Embolism and Compartment Syndrome

The differential diagnosis for lower extremity swelling and ankle pain is broad and can have overlapping and related diagnoses. If there is concern for more than one diagnosis, the practitioner should perform a thorough physical examination, order the appropriate studies, and perform the correct procedures to completely diagnose and treat the patient. This article presents the case of a 19-year-old male who presented with 5 days of left ankle pain, fevers, and swelling without any known trauma to the area. Physical examination was concerning for a septic ankle joint, cellulitis, deep venous thrombosis, and compartment syndrome. Duplex venous ultrasound confirmed a deep venous thrombosis in the popliteal vein. Joint aspiration of the ankle had gross purulence with the presence of methicillin-resistant Staphylococcus aureus. The patient was taken emergently to the operating room where he was found to have gross purulence in the deep posterior compartment, medial and lateral soft tissues of the ankle, and gross purulence in the ankle joint. The deep posterior compartment also had significant muscle necrosis and evidence of compartment syndrome. This case presents the possibility of a septic ankle leading to compartment syndrome and deep venous thrombosis/pulmonary embolism due to the intra-articular nature of the flexor hallucis longus tendon sheath. Level of Evidence: Case report, Level IV