Flexor Hallucis Brevis

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Description: 

Flexor hallucis brevis is one of the third layer (of four layers) of plantar muscles. It is located adjacent to the plantar surface of the 1st metatarsal.  

Origin:

Lateral part of the muscle is originated medically to the cuboid bone and laterally to the cuneiform bone.

Medial part of the muscle is originated from the tendon of tibialis posterior.

Insertion:

Both parts of the muscle are inserted on the hallux (sides of the base of proximal phalanx). The medial part pleads with the abductor hallucis muscle and the lateral part blends with the adductor hallucis muscle.

Nerve:

Nerve root S1-S2

Medial plantar nerve 

Artery:

Supplied by branches of the posterior tibial artery 

Function

Flexion of the great toe at the metatarsophalengial joint 

Assessment

Palpation: 

It is nearly impossible to palpate the FHB muscle while it is located deeply in the foot. (The third layer from 4 layers of the foot muscles).

Muscle strength: 

As usual, the FHB strength can be measured manually by MMT grading. Start the test by having the patient in supine/long sitting position with the foot hanging over the table. With your hand, hold the foot just below the ankle for stabilization and ask him/her to bent the big toe while you resist the movement by your fingers of the other hand and start the grading.

Treatment

Strengthening: 

Pulling the towel would always be the good option for strengthening the big toe and other four toes flexors, but make sure that the patient is using the FHB muscle so she/he should flex the great toe by bending it at the MP joint. You can progress the exercise by putting a little heavy object on the towel. 

Stretching:

Stretch the muscle by moving the big toe into hyper extension as much as possible, hold then relax.