Flexor Hallucis Longus Bursa

bursa tendinis musculi flexoris hallucis longi

The flexor hallucis longus tendon sheath is the synovial sleeve around the FHL tendon as it runs through a fibro-osseous tunnel behind the talus and under the sustentaculum tali. It lets the tendon glide as it turns toward the big toe. It often communicates with the ankle joint, and inflammation here (FHL tenosynovitis) is a classic cause of posterior ankle pain in dancers.

Anatomical Data

Boundaries & Contents

Location	Back and inner side of the ankle, from behind the talus to beneath the sustentaculum tali
Boundaries	Groove between the medial and lateral tubercles of the posterior talar process Groove under the sustentaculum tali Flexor retinaculum and fibrous tunnel roof
Contents	Flexor hallucis longus tendon

Biomechanics

Function & Actions

Lets the FHL tendon glide through its fibro-osseous tunnel as it turns into the sole. It communicates with the ankle joint in some people, and tenosynovitis here is common in ballet dancers.

Clinical Relevance

Clinical Notes

Flexor hallucis longus bursitis occurs in ballet dancers, gymnasts and others who perform repetitive forced plantarflexion, particularly in the en pointe position, and often forms part of posterior ankle impingement syndrome. The bursa can communicate with the ankle joint, explaining why FHL-related symptoms may coexist with posterior ankle impingement. Ultrasound and MRI demonstrate fluid around the FHL tendon in the posterior ankle groove. Posterior ankle arthroscopy allows simultaneous FHL tendon release, bursal excision and removal of an os trigonum.

Pathology

Common Injuries & Conditions

Posterior Ankle FHL Bursitis

Bursal and tenosynovial inflammation around the FHL in the posterior ankle groove, producing posterior ankle pain during plantarflexion in dancers and athletes, managed with activity modification, physiotherapy, and posterior ankle arthroscopy for refractory cases.

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