What is the diagnosis and treatment for myositis of the flexor hallucis longus (FHL) muscle?

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Last updated: March 25, 2025View editorial policy

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From the Guidelines

Treatment for myositis of the flexor hallucis longus (FHL) muscle should prioritize physical therapy, incorporating stretching and strengthening activities, to regain muscle strength and function, as well as to reduce inflammation, as evidenced by studies such as 1. The diagnosis of myositis of the FHL muscle typically involves a combination of physical examination, medical history, and potentially imaging studies to rule out other causes of foot pain. Key aspects of treatment include:

  • Rest and ice application to reduce acute inflammation
  • Non-steroidal anti-inflammatory drugs (NSAIDs) for pain management, such as ibuprofen or naproxen, for a short duration (1-2 weeks) as needed
  • Physical therapy is crucial and should be initiated early, focusing on gentle exercises that stretch and strengthen the FHL muscle, as intensive resistance training has been shown to be beneficial and safe in patients with similar conditions 1
  • Proper footwear with adequate arch support to reduce strain on the FHL muscle
  • Activity modification to avoid exacerbating the condition, particularly during the initial 2-4 weeks of treatment In cases where symptoms persist or worsen, further evaluation with imaging (ultrasound or MRI) may be necessary to assess for complications such as tendon tears. Severe cases might require additional interventions like immobilization with a walking boot or corticosteroid injections, but these should be considered after initial conservative management has failed. The goal of treatment is to alleviate pain, restore function, and prevent long-term disability, with a focus on early initiation of physical therapy to improve outcomes, as supported by the principles outlined in 1.

From the Research

Diagnosis of Myositis of the Flexor Hallucis Longus (FHL) Muscle

  • The diagnosis of myositis of the FHL muscle is typically based on the patient's history and physical examination, including tenderness along the tendon, particularly at the fibroosseous tunnel 2.
  • Imaging studies, such as CT scans, may also be used to evaluate the location of contrast material injected into the FHL tendon sheath 3.
  • The condition can be related to trauma, and is not exclusive to ballet dancers or overuse 4.

Treatment of Myositis of the FHL Muscle

  • Conservative management, including soft tissue and joint mobilization, laser therapy, kinesiology tape application, and rehabilitative exercise, can be effective in treating FHL stenosing tenosynovitis 5.
  • A specific stretching protocol for FHL tendonitis has been shown to reduce symptoms and decrease the need for surgery 2.
  • Corticosteroid injections into the FHL tendon sheath can be used as a conservative treatment, and can be administered with high accuracy using a blind injection technique based on clinical examination 3.
  • Arthroscopic release of the FHL tendon is a valid procedure for treating FHL tenosynovitis, and can provide good results with minimal complications 4.
  • Surgical intervention, such as open release of the FHL tendon, may be necessary in cases where conservative treatment fails 4, 6.

Factors Associated with Treatment Outcomes

  • Completion of a specific FHL stretching program is associated with a decreased likelihood of needing surgery 2.
  • Clinical hallux rigidus and posteromedial ankle pain are associated with an increased likelihood of needing surgery 2.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

The accuracy of an injection technique for Flexor hallucis longus tendon sheath: A cadaveric study.

Foot and ankle surgery : official journal of the European Society of Foot and Ankle Surgeons, 2020

Research

Tenosynovitis of the flexor hallucis longus in a long-distance runner.

Medicine and science in sports and exercise, 1996

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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