Flexor hallucis longus (FHL) tendinopathies encompass a spectrum of conditions that are being increasingly recognized in clinical practice.
Flexor hallucis longus (FHL) tendinopathies encompass a spectrum of conditions that are being increasingly recognized in clinical practice. Patients typically present with posteromedial ankle pain and localized tenderness along the course of the FHL tendon. Diagnostic imaging, particularly MRI and ultrasound, can help confirm the diagnosis and assess the extent of pathology.
Management is usually conservative, focusing on physical therapy, activity modification, and periods of immobilization when necessary. Intersection syndrome of the foot is a poorly understood condition characterized by fibrosis where the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) intersect at the Knot of Henry, often related to repetitive hyperextension of the first metatarsophalangeal joint or partial FHL tearing. FHL rupture or laceration is rare and reported mainly in case studies, occurring from traumatic or atraumatic causes at sites such as the metatarsal headâneck junction, plantar first phalanx, Knot of Henry, talar groove, or beneath the sustentaculum tali; patients present with sudden severe pain, weakness, and loss of great toe flexion, with MRI confirming the diagnosis and surgical repair recommended for complete ruptures.
Stenosing tenosynovitis results from chronic inflammation and mechanical irritation of the FHL within its fibro-osseous tunnelâmost commonly at the posterior ankle under the sustentaculum taliâdue to repetitive microtrauma and high plantarflexion loads, such as forefoot push-off or en pointe positioning in ballet, with less common involvement near the sesamoids or proximal to the medial malleolus.Flexor hallucis longus (FHL) pathology most commonly results from overuse and tendinosis associated with activities involving maximal plantarflexion and repetitive forefoot push-off, particularly in dancers. In ballet, repeated transitions from pliĂ© (bending) to relevĂ© (rising onto the toes), especially in en pointe, place the ankle in a loaded hyperplantarflexed position that can kink and compress the FHL as it enters the fibro-osseous tunnel posterior to the talus. Acute FHL lacerations may also occur traumatically.
In stenosing tenosynovitis, symptoms are thought to arise within the fibro-osseous tunnel due to either relative incongruity between the tendon and tunnel during full plantarflexionâcreating abnormal stress under extreme tensionâor distal tendon excursion during ankle and hallux dorsiflexion, where a low-lying muscle belly becomes jammed within the tunnel, leading to inflammation and swelling. Flexor hallucis longus (FHL) pathology is commonly associated with posterior ankle impingement, os trigonum syndrome, hallux rigidus, plantar fasciitis, and tarsal tunnel syndrome, with significant overlap in clinical presentationâup to 74% of patients may demonstrate two or more concurrently. Hallux rigidus appears to have an etiologic relationship with FHL disorders and increases the likelihood of requiring surgical treatment.
Anatomically, the FHL originates in the deep posterior compartment of the leg from the distal two-thirds of the posterior fibula, interosseous membrane, posterior intermuscular septum, and fascia of tibialis posterior, and inserts on the base of the distal phalanx of the great toe. It primarily plantarflexes the hallux at the IP and MP joints and secondarily assists ankle plantarflexion, passing through the tarsal tunnel into the foot. At the Knot of Henry in the midfoot near the navicular, the flexor digitorum longus tendon crosses superficially over the FHL, with variable distal interconnections between the two tendons.
If you are experiencing symptoms that may be related to flexor hallucis longus tendinopathy, it is important to see a sports medicine physician. Early evaluation and treatment typically lead to better outcomes. Do not ignore pain or symptoms that are limiting your activity.
*This article is for educational purposes only and does not substitute for professional medical advice. Always consult a qualified healthcare provider.*
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