200 Section - Successful Ultrasound-Guided Injection for Flexor Hallucis Longus Tenosynovitis at the First Metatarsophalangeal Joint: A Case Report

Wednesday, May 20, 2026

6:00 PM - 7:30 PM PT

Presenting Author/Autor expositor(s)

HA

Hanna Asheber, BS

Medical Student
University of Toronto
Toronto, Ontario, Canada
AL

Alyssa Lee, MD

Resident
University of Toronto
Toronto, Ontario, Canada

Co-Author/Coautor(s)

JF

Jordan Farag, MD

Physiatrist, Assistant Professor
Toronto Rehabilitation Institute, University of Toronto
Toronto, Ontario, Canada

Case Diagnosis: Flexor hallucis longus (FHL) tenosynovitis is an uncommon cause of medial foot and posterior ankle pain, typically associated with activities requiring repetitive plantarflexion. While most cases involve the retrotalar groove or mid-tendon, FHL tenosynovitis localized to the first metatarsophalangeal (MTP) joint is exceedingly rare. This report describes a case of symptomatic FHL tenosynovitis at the level of the MTP joint successfully treated with an ultrasound-guided corticosteroid injection.

Case Description: A 28-year-old male with ulcerative colitis presented with a one-year history of insidious plantar first MTP pain. Examination revealed swelling, erythema, and warmth over the FHL tendon at the MTP level. Diagnostic ultrasound confirmed FHL tenosynovitis, most prominent at and proximal to the joint. Under ultrasound guidance, a 30-gauge needle was used to anesthetize the skin, followed by in-plane advancement of a 25-gauge needle into the tenosynovium. A total of 20 mg methylprednisolone was injected into the tendon sheath with real-time visualization. The procedure was well tolerated without complications. At two-week follow-up, the patient reported approximately 75% improvement in pain, and a gradual return to activity was recommended.

Discussions: FHL tenosynovitis is increasingly recognized as a contributor to foot and ankle pain, though pathology at the MTP level is rarely described. Its presentation may mimic other forefoot pathologies, underscoring the need for detailed anatomical assessment and targeted diagnostic imaging. Ultrasound enables high-resolution visualization of the tendon sheath, facilitating precise needle placement and supporting both diagnostic clarity and therapeutic interventions.

Conclusions: To our knowledge, this is the first reported case of ultrasound-guided injection for FHL tenosynovitis at the MTP joint. This case highlights the importance of considering FHL pathology in atypical locations and demonstrates the value of a physiatric, ultrasound-guided approach in identifying and treating uncommon musculoskeletal pain generators.