Lower limb
Tendon sheath of flexor hallucis longus
Vagina tendinis musculi flexoris hallucis longi
- Origin
- Begins at the level of the posterior ankle joint line
- Insertion
- Passes through the posterior talar groove beneath the sustentaculum tali and extends along the sole to the distal phalanx of the hallux
- Function
- Provides low-friction gliding for the flexor hallucis longus tendon, the key engine of toe-off propulsion
- Innervation
- Branches from the tibial nerve
- Movement & chain
- Under intense stress during extreme ankle plantarflexion combined with hallux extension (ballet 'en pointe')
- Palpation
- Palpable posteromedially behind the ankle beneath the sustentaculum tali
- Clinical
- FHL tenosynovitis ('Dancer's tendinitis' / trigger toe); posterior ankle impingement syndrome (os trigonum syndrome)
- Segmental innervation
- L5, S1, S2 spinal segments
- In clinical practice
- Posterior ankle impingement evaluation; ultrasound-guided sheath injection and posterior ankle arthroscopic decompression/os trigonum excision
- Region in the model
- Lower limb