The Flexor Hallucis Longus

Flexor Hallucis Longus

One of the key extrinsic muscles responsible for flexion of the hallux and stabilisation of the medial longitudinal arch, the flexor hallucis longus originates from the lower two-thirds of the posterior fibula.

The tendon runs posterior to the medial malleolus in a sheath; this sheath courses between the medial and lateral tubercles of the posterior aspect of the talus.

The flexor hallucis longus inserts itself into the distal phalanx of the hallux after passing under a fibro-osseous tunnel to the sustentaculum tali; the occurrence of injuries to the flexor tendon commonly happens due to constriction of the fibro-osseous tunnel.

The hallux flexor muscles can play a critical role in enhancing sports performances because of their potential to produce maximal amounts of force transference from the foot to the ground in the push-off phase of the gait cycle.

A study conducted by Jacob H.A., of the Department of Orthopaedic Surgery at the University of Zurich, further explored the forces acting along the flexor tendons and joints of the forefoot during motion.

Anthropometrical data was combined with data on ground force distribution during the second force peak of the stance phase, in order to record equilibrium in the first sagittal plane for the joints of the first and second rays.

The flexor hallucis longus was observed to exert around 52% of the body weight in the gait cycle, while the total force acting on the first metatarsal head during push-off was determined to be about 119% of the bodyweight.

This implies that imbalances in the functioning of the flexor hallucis longus can cause disruption in the high forces that run along the flexor tendons of the first ray during gait; these are the forces that support the medial longitudinal arch of the foot.

A collapse in the medial longitudinal arch will result in a number of pathological deformities such as Plantar Fasciitis and Hallux Valgus, due to the diminished ability of the foot in sustaining the weight of the body and absorbing majority of the shock forces from the ground.

MASS4D® foot orthotics are calibrated to stabilise the medial longitudinal arch by allowing both the intrinsic and extrinsic muscles of the foot to work well within their full range of motion. This builds strength in these muscles to achieve optimal functionality of the hallux and the foot in general.

Related Links


  1. Annamária Péter, András Hegyi, József Tihanyi, Neil Cronin (2016) Function of the Flexor Hallucis Longus Muscle – What Do We Know?. ResearchGate. Retrieved from:
  2. Jacob H.A. (2001) Forces Acting in the Forefoot During Normal Gait--An Estimate. Clinical Biomechanics: November 2001, Vol. 16, No. 9, pp. 783-792

Copyright 2016 MASS4D® All rights reserved.