summary FHL Tendonitis & Injuries occur as a result of impingement of the flexor hallucis longus tendon with resultant tendonitis and even tendon rupture along the posterior ankle joint. Diagnosis can be made clinically with posteromedial ankle pain and pain with resisted flexion of the hallux IP joint. MRI studies may show tenosynovitis of the tendon. Treatment is generally rest, activity modifications and NSAIDs. Surgical management is indicated for acute FHL tendon laceration and progressive tendonitis that fails nonoperative management. Epidemiology Anatomic location posterior ankle great toe Risk factors excessive plantar-flexion dancers in on pointe position gymnasts Etiology Pathophysiology mechanism of injury activities involving maximal plantar-flexion pathoanatomy posterior to the talus within the fibro-osseous tunnel in chronic cases nodule formation may lead to triggering Associated conditions posterior ankle impingement os trigonum (posterolateral tubercle) Anatomy Muscle FHL originates from posterior fibula travels between posteromedial/posterolateral tubercles of the talus contained within fibro-osseous tunnel passes beneath the sustentaculum tali crosses dorsal to FDL (at the Knot of Henry) FHL is "higher" at Knot of Henry FDL is "down" at Knot of Henry multiple connections exist between the FDL and FHL distally it stays dorsal to the FDL and neurovascular bundle inserts on the distal phalanx of the great toe Biomechanics primary action plantarflexion of the hallux IP and MP joints secondary action plantarflexion of the ankle Presentation Symptoms posteromedial ankle pain great toe locking with active range of motion crepitus along the posterior medial ankle Physical exam pain with resisted flexion of the IP joint pain with forced plantarflexion of the ankle motion great toe triggering with active or passive motion but no tenderness at the level of the first metatarsal head Imaging MRI findings fluid around the tendon at level of ankle joint intra-substance tendinous signal Differentials Os trigonum syndrome pain is posterolateral in os trigonum syndrome Treatment Nonoperative rest/activity modification, NSAIDS indications first line of treatment modalities arch supports physical therapy Operative release of the FHL from the fibro-osseous tunnel, tenosynovectomy, possible tendinous repair indications recalcitrant symptoms in athletes when symptoms persist despite rest and nonsurgical management technique approach arthroscopic open, posteromedial FHL Laceration Introduction direct trauma to the FHL tendon in an acute setting Pathophysiology mechanism of injury acute laceration most common form of injury Presentation physical exam range of motion loss of active interphalangeal joint flexion Imaging MRI findings tendon ends may be retracted Treatment operative acute surgical repair of the laceration indications lacerations of both the FHL and the FHB